Cause of PL Coins

[newprepper]

I didn't want to hijack another thread soI will ask my question here regarding Proof Like coins. What conditions cause them? Are they more likely to occur when a die is new or does the die self polish (from the action of the metal flowing) from use? Or is it more a condition of the planchet? I ask because I saw a documentary on the Hubble telescope and the final grind or polish was accomplished by rubbing your thumb on the mirror. They could only rub it for a few seconds every couple of days because the mirror had to be a certain temp for the measurements and the action of rubbing it caused it to heat up. Or something to that effect.

[RWB]

Working dies were occasionally smoothed with an abrasive-charged disc or wheel. This was done to remove minor surface damage - cracks and clash marks - and sometimes to adjust the curvature (or "basin") of the field. The appearance of the fields after abrading depended on the abrasive used. The normal abrasive was "flour emery" (aka "crocus"), but finer and coarser abrasives were occasionally used, too. This produced a somewhat mirrored surface that collectors call "proof-like" as it resembles a true proof surface.

 

Some of the die repair was done by the engraving department's die sinkers, and some was done in the press room by die setters.

 

As a die was used, the semi-mirror surface gradually altered to be similar to the average of planchets. The more pronounced the mirror-like effect, the more quickly it deteriorated.

 

[The new book “From Mine to Mint” (available in January) has details about abrasives, repairs and other die-related subjects.]

 

[JVC]

I am only familar with morgan dollars. PL morgans resulted when the new dies were initially basined and polished at each mint prior to beginning production. The initial coins would show PL surfaces until they became worn. PL morgans were also produced when worn dies were polished to repair defects that developed after production had started.

[BillJones]

Not all new dies produce P-L coins. The New Orleans mint did such a bad job with their die preparation in the 1890s that many dies produced dull, lifeless coins from the time they came together until the end.

[newprepper]

Do you see the dies producing PL coins today, or is the manufacture of them at a point that it doesn't happen any longer?

[RWB]

New dies were not mirror finished, unless they had to be adjusted or repaired before use. Many of the SF dies were over-adjusted for basin and this created a lot of semi-mirror working dies. The normal original surface of a Morgan die is smooth. This was created by the hub light final abrasion.

[RWB]

Modern working dies get a quick surface cleanup - usually with a medium abrasive pad....so PLs could occur.

[physics-fan3.14]

There are many different era's of PL coinage, and each have a different cause (and appearance). The techniques that Roger described are particularly geared towards late 19th century PL's (Morgans and Seated Liberty types).

 

Modern PL's (starting in the 1980's) are created from fresh new dies. These are all chrome plated and have a mirror finish when new. These PL strikes don't last too long, but sometimes the mirrors can be quite strong (rarely, the coins will have DMPL mirrors).

[newprepper]

Lets see if I understand this at least partially, the flowing of the metal during the strike actually roughens up the surface of the die over time removing the PL appearance. So a new or newly re-surfaced die will have the best chance of producing a PL appearance.

[physics-fan3.14]

Lets see if I understand this at least partially, the flowing of the metal during the strike actually roughens up the surface of the die over time removing the PL appearance. So a new or newly re-surfaced die will have the best chance of producing a PL appearance.

 

Yes.

[RWB]

Modern coatings for coinage dies emulate the original die surface and do not impose a mirror surface. Because the surface coating is very hard and durable, if what you suggest were done, collectors would see millions of "PL" quarters, dimes, halves, etc. Chromium plating has not been used for nearly a decade.

 

(PS: I've watched the complete modern hub creation to die setting processes, including the mint's Micron cutting tools and cathodic arc deposition techniques. Fascinating stuff, but not along the lines of research of interest to me.)

 

[Conder101]

The normal original surface of a Morgan die is smooth. This was created by the hub light final abrasion.

But wouldn't at least some polishing of the new die be required to remove the oxides left on the surface from the final heat treating and hardening process?

[JVC]

Conder,

 

I agree with you that some polishing was done on each new die before coins were struck. I believe this polishing cause the majority of the DMPL and PL morgans.

 

[RWB]

Conder - The dies were hardened in a nonoxidizing atmosphere. They were quenched in cold water using a special apparatus that cooled the face first. There was almost no surface oxidation damage. The primary problem was occasional change in die radius – which could end up with a semi-mirror surface depending on local conditions.

 

After cooling and inspection, the die was lightly cleaned with medium abrasive - not fine enough to bring up a semi-mirror polish, unless, of course, the wrong abrasive was used.

 

It’s easy to think that dies started out highly polished and then degraded with use. However, that view has never been supported by factual research and analysis. It is a “seat of the pants” guess based on incomplete, or totally absent, contemporary information.

 

Collectors might believe as they wish - all the "bare breasted" SL quarter nonsense is a good example - but the normal operating procedures are consistent with semi-mirror/PL surface being a post-production artifact.

[newprepper]

Thanks all, pretty informative

[cladking]

There are numerous conditions which cause or can contribute to what we call "Proof Like". Basining of dies is the most recognizable and the most common throughout different eras of production. This is the "flattening" of the dies' surfaces which often causes struck coins (especially early strikes) to exhibit mirror like properties as most proofs have. Even new dies that haven't been basined can produce some very PL coins after they have worn smooth if a polished or partially polished planchet is struck. Before the dies wear smooth they will produce something that looks more like a matte proof under ideal conditions. There's a lot going on when a coin is struck and the result depends on each parameter from speed, strike pressure, alignment, and die/ planchet condition. Even minor parameters like vibrations, temperature, or lubrication can cause big differences in the appearance of successive coins. Die and planchet preparations and conditions are most easily seen on the struck coin and it is these that most contribute to a coin being PL or not. The single largest factor is in die preparation from hubbing to basining and the condition of the die when it strikes a coin.

[RWB]

I realize folks are trying to present the best information they have – the difficulty is that the old info is sometimes wrong, misleading or misunderstood. Some corrections from modern research might help.

 

There are numerous conditions which cause or can contribute to what we call "Proof Like".

1. Basining of dies is the most recognizable and the most common throughout different eras of production.

2. This is the "flattening" of the dies' surfaces which often causes struck coins (especially early strikes) to exhibit mirror like properties as most proofs have.

3. Even new dies that haven't been basined can produce some very PL coins after they have worn smooth

4. if a polished or partially polished planchet is struck. Before the dies wear smooth they will produce something that looks more like a matte proof under ideal conditions.

 

1) Very few collectors – including some of the best Morgan dollar experts – can identify an improperly basined die. The series of 1878-S dollars with crudely scratched wing feathers are all from improperly basined reverse dies; most others are difficult.

2) The basin of a die is its convex curvature…part of the geometry. Curvature of itself does not alter the texture of the die surface.

3) All nineteenth century and most twentieth century working dies were MADE with a specific radius of curvature (called the die basin). This was supposed to be common to all dies for each side of a design. The initial basin is part of the hub’s geometry. Only if corrections were necessary, was a die abraded to alter the radius of curvature. (Gobrecht used 24-inches based on measurements of coins Franklin Peale brought back from Europe. See his letter of March 8, 1836.)

4) I don’t understand your comments – When it is struck, a planchet is forced to conform to the hard steel die surface, not the other way around. If there is an isolated mirror planchet it will still come out of the press looking like any other coin. It certainly has nothing to do with sandblast proof or matte proof surfaces….

The remaining comments are incomprehensible to me….sigh….

 

[cladking]

I1) Very few collectors – including some of the best Morgan dollar experts – can identify an improperly basined die. The series of 1878-S dollars with crudely scratched wing feathers are all from improperly basined reverse dies; most others are difficult.

 

Not all dies are basined at all. I believe you're speaking primarily about classic US coins and I'm trying to address the question much more generally to include all coins or tokens that exhibit PL characteristics.

 

Many dies pretty much go from annealing and hubbing straight to coining.

 

2) The basin of a die is its convex curvature…part of the geometry. Curvature of itself does not alter the texture of the die surface.

 

Yes, most dies that struck old US coins that were basined actually had a curvature with a large radius. This varies from place to place and time to time.

 

4) I don’t understand your comments – When it is struck, a planchet is forced to conform to the hard steel die surface, not the other way around. If there is an isolated mirror planchet it will still come out of the press looking like any other coin. It certainly has nothing to do with sandblast proof or matte proof surfaces….

The remaining comments are incomprehensible to me….sigh….

 

New dies do not make as shiny coins as those which have been in operation even briefly. If new dies slowly strike a polished planchet it can make a PL coin even without basined dies. It won't have mirrors but will otherwise appear PL.

 

I believe a better way to picture the coining process is that the dies "attempt" to make the planchet conform to them. In actuality it's a two way street and the planchet rarely fills the entire die even on old US coins.

[e1cnr]

Sometimes proof dies were grabbed by mistake for the day, or they were done striking proofs and retired the die to business strikes.

[physics-fan3.14]

3) All nineteenth century and most twentieth century working dies were MADE with a specific radius of curvature (called the die basin). This was supposed to be common to all dies for each side of a design. The initial basin is part of the hub’s geometry. Only if corrections were necessary, was a die abraded to alter the radius of curvature. (Gobrecht used 24-inches based on measurements of coins Franklin Peale brought back from Europe. See his letter of March 8, 1836.)

 

Seated Liberty and Morgan's might all have the same die radius. But once the coinage was redesigned, the Lincoln, Buffalo, and Merc all have extremely different radii.

[RWB]

cladking, e1cnr, physics-fan3.14 ---

 

Let’s try one more – final – time. (Maybe the problem is that I’m not communicating very well, or maybe that there are important parts of making and using dies are you’re not understanding – it’s probably my fault.)

 

Re: Many dies pretty much go from annealing and hubbing straight to coining.

 

That’s correct – because the curvature is part of the shape of the hub. If the die did not deform, then its radius (“basin”) remained correct and nothing would be done to change it.

 

Re: New dies do not make as shiny coins as those which have been in operation even briefly. If new dies slowly strike a polished planchet it can make a PL coin even without basined dies. It won't have mirrors but will otherwise appear PL.

 

Huh? The question was about PL coins not shiny ones. The second half of your statement is completely wrong—“mirrors” are PL – or approximations thereof.

 

Re: I believe a better way to picture the coining process is that the dies "attempt" to make the planchet conform to them. In actuality it's a two way street and the planchet rarely fills the entire die even on old US coins.

 

Dies striking a single polished planchet, or a small quantity, will NOT produce PL coins. The die is much harder than the softened planchet. The die will very gradually conform to the average surface of the planchets – if they are all polished, then the die will eventually exhibit semi-mirror surfaces over ALL of the face – fields, lettering and portrait. (A good modern example are the so-called PL $20 small diameter pieces the mint made. The smooth dies gradually conformed to the surface of polished planchets. The dies were not polished.) No one is talking about filling the die – that had nothing to do with getting a semi-mirror surface.

 

Re:Sometimes proof dies were grabbed by mistake for the day, or they were done striking proofs and retired the die to business strikes.

 

No. Proof dies were (after about 1850) carefully polished and kept in separate locked cabinets, precisely so there would be no mix-ups.

 

Re: Seated Liberty and Morgan's might all have the same die radius. But once the coinage was redesigned, the Lincoln, Buffalo, and Merc all have extremely different radii.

 

Yikes. No one said that SL and Morgan dollars had the same radius. Gobrecht was mentioned in an 1836 letter. Most designs had different radii, and those changed over time as equipment changed. Go read my Renaissance of American Coinage books if you want to learn about the problems associated with designs that did not have a defined radius. This was a major point of contention between Charles Barber and Saint-Gaudens/ Weinman/ MacNeil, etc.

 

[cladking]

Huh? The question was about PL coins not shiny ones. The second half of your statement is completely wrong—“mirrors” are PL – or approximations thereof.

 

I think this is much of the problem; we aren't defining PL the same. If you define it only as mirror surfaces a lot of coins with unusual and PL characteristics are excluded. Most old US coins that are PL are because of mirrors but this is less apllicable to modern PL's and other series of coins and tokens.

 

The grading services seem to agree with your definition in my very limited experience.

 

Dies striking a single polished planchet, or a small quantity, will NOT produce PL coins.

 

In my experience a polished planchet struck by a die will look different than a regular planchet. It won't necessarily look very PL but it can if the other characteristics of the coin are consistent with proof coins. If the dies are new and the strike is very clean there can even be squared rims. If a few characteristics of proofs come together it can appear PL (by my definition) without mirrors.

 

Modern dies are not so cut and dried as with the older ones. They don't each recieve exactly the same treatment.

 

You're probably not wrong about anything (I may well be) but our perspectives are very different because I look at large numbers of early die state modern coins. One just gets a different perspective on dies by seeing so many different early die states. All dies are not created equal and the resultant coins can vary dramatically. All these differences are not in die preparation though, and some are apparently in planchet conditions and other parameters. A lot of factors have to come together to get a well struck Gem but it takes different factors to make one of a countless number of types of PL's.

 

 

 

 

 

 

[e1cnr]

Re:Sometimes proof dies were grabbed by mistake for the day, or they were done striking proofs and retired the die to business strikes.

 

No. Proof dies were (after about 1850) carefully polished and kept in separate locked cabinets, precisely so there would be no mix-ups.

 

 

 

 

Then why is it there are so many varieties in many series where a business strike is made with a proof die?

 

mpls, type 2 rev quarters, type 2 rev IKEs, type 2 rev Franklins,....

[newprepper]

cladking, e1cnr, physics-fan3.14 ---

 

Let’s try one more – final – time. (Maybe the problem is that I’m not communicating very well, or maybe that there are important parts of making and using dies are you’re not understanding – it’s probably my fault.)

 

Re: Many dies pretty much go from annealing and hubbing straight to coining.

 

That’s correct – because the curvature is part of the shape of the hub. If the die did not deform, then its radius (“basin”) remained correct and nothing would be done to change it.

 

Re: New dies do not make as shiny coins as those which have been in operation even briefly. If new dies slowly strike a polished planchet it can make a PL coin even without basined dies. It won't have mirrors but will otherwise appear PL.

 

Huh? The question was about PL coins not shiny ones. The second half of your statement is completely wrong—“mirrors” are PL – or approximations thereof.

 

Re: I believe a better way to picture the coining process is that the dies "attempt" to make the planchet conform to them. In actuality it's a two way street and the planchet rarely fills the entire die even on old US coins.

 

Dies striking a single polished planchet, or a small quantity, will NOT produce PL coins. The die is much harder than the softened planchet. The die will very gradually conform to the average surface of the planchets – if they are all polished, then the die will eventually exhibit semi-mirror surfaces over ALL of the face – fields, lettering and portrait. (A good modern example are the so-called PL $20 small diameter pieces the mint made. The smooth dies gradually conformed to the surface of polished planchets. The dies were not polished.) No one is talking about filling the die – that had nothing to do with getting a semi-mirror surface.

 

Re:Sometimes proof dies were grabbed by mistake for the day, or they were done striking proofs and retired the die to business strikes.

 

No. Proof dies were (after about 1850) carefully polished and kept in separate locked cabinets, precisely so there would be no mix-ups.

 

Re: Seated Liberty and Morgan's might all have the same die radius. But once the coinage was redesigned, the Lincoln, Buffalo, and Merc all have extremely different radii.

 

Yikes. No one said that SL and Morgan dollars had the same radius. Gobrecht was mentioned in an 1836 letter. Most designs had different radii, and those changed over time as equipment changed. Go read my Renaissance of American Coinage books if you want to learn about the problems associated with designs that did not have a defined radius. This was a major point of contention between Charles Barber and Saint-Gaudens/ Weinman/ MacNeil, etc.

 

So part of what you are saying, is that if polished planchets were used, they in effect polished the dies thereby making it posible for them to produce PL coins. I think.......my brain hurts

[physics-fan3.14]

I'm just trying to understand, Roger. Thanks for clearing things up. It seems like a lot of what I "knew" about PL's is wrong - but I still love them.

 

And, because what is a thread about prooflikes without a couple of pictures, here is a Feldini special, photog'd by Bob Campbell.

 

[newprepper]

Now to me, the front does not appear as PL as the reverse, but that is one nice dime. love the toning

[RWB]

Very nice dime -- reminds me of the ones Kam Ahwash used to find.

 

newprepper –

 

So part of what you are saying, is that if polished planchets were used, they in effect polished the dies thereby making it possible for them to produce PL coins. I think.......my brain hurts.

 

Yep – except the mirror would be over the entire coin, not just the fields.

 

Another example are proof Franklin halves. The new dies were lightly cleaned with acid . This created “frost” over the entire surface (much as seen on some Morgans). The engraver then coated the entire die with a tough frisket material, and then cut away the frisket protecting the fields. This left the lettering and portrait protected and the fields exposed.

 

The fields were then polished to mirror smoothness by using a range of abrasives and various tools – even down to sticks of wood and charcoal. The polished die was then cleaned of all dirt, abrasive and remaining frisket material, and was ready for use in a medal press to make proof coins.

 

Proof coin planchets were polished to a mirror surface before use. The mint thought this produced better proofs and minimized defects in the coins. As proof coins were struck the hard die surface moved the metal on the planchet so that the coin adopted the die’s surface. For the first hundred or so coins, the frosted portrait and mirror fields produced what we now call “cameo” proofs.

 

But, even though die steel was very hard, it was not impervious to change. We usually think of these changes a flow lines which create luster, On a Franklin proof die, the mirror fields rubbed against the mirror planchets, and there were little changed. But the frosted portrait gradually became mirrored as it rubbed against the mirror surfaces of hundreds of planchets. The frost was not very durable, and soon all the coins were mirrored, like the planchets, over their entire surface.

 

[JVC]

Leroy C. Van Allen and George Mallis in the]Comprehensive Catalog and Encyclopedia of Morgan and Peace Dollars (1991) described the preparation of the dies. "Basining of the Morgan dollar working dies was performed at each mint prior to their being placed in the presses. It consisted of putting the dies upright in a fixture which held the die face against a slightly dished die face making it slightly convex. The radius of this curvature varied with each mint and caused the planchet metal to flow more toward the coin rim or coin center in extreme cases. This resulted in the weakly struck center coins with full rims typical of the New Orleans Mint or fully struck center design and rounded rims typical of the San Francisco Mint."

 

"A polishing grit compound was used in the basining process. The depth of mirror on the die face was a function of how fine a compond was used during the basining process and also if a final buffing of the die face was performed. Thus, the degree of mirror initially on the die varied from mint to mint over the years and at a particular mint with time because of the different workmen and practices enforced."

 

"As basined and polished die struck coins, the friction of the plancet metal moving against the die field would wear the die surfaces making them dull. The mirror surface would gradually be less and less reflective until it became semi-proof and finally dull with no reflection."

 

Q. David Bowers in A Guide Book of Morgan Silver Dollars (2012) also describes the preparation of the dies before coins were struck.

 

"The working die was then hardened. The heating and cooling treatment in the hardening and softening (annealing) process sometimes resulted in scale or rough spots on the face of the working die. The working-die-in-process was then taken to a machine to be basined, as described earlier, While some dies for branch mints may have been basined at Philadelphia, many if not most were basined, or given extra basining, at the branch mints, as each had a machine shop."

 

Depending upon the fineness of the grit used in the zinc receptical, and the length of time basining, working dies acquired surfaces ranging from smooth and clean, to slightly polished (creating what we call semi-prooflike coins today), to more polished (prooflike), or even further, to impart a deeply mirrored surface (deep mirror prooflike, or DMPL, is the term used today)."

 

"Although the details are not known to have been recorded, it is likely that DMPL coins were made by simply leaving a working die in the basining machine for an overly long time, no doubt inadvertently."

 

These experts seem to confirm that many PL/DMPL morgans were the result of the initial preparation of the working dies.

 

 

[RWB]

It’s great that some time was invested in researching this, but big pieces – including your final assumption – are wrong.

 

Re: VanAllen & Mallis quotes.

Paragraph 1 is mostly wrong.

Paragraph 2 is correct except as it implies that semi-mirror surfaces were part of NEW dies – that is wrong.

Paragraph 3 is correct.

 

Re: Dave Bowers quotes.

Paragraph 1 is partially wrong. The die radius was determined by the radius of the hub and any distortion that might occur during final hardening. Only San Francisco and Carson were sent soft dies and that was to adjust the shank to fit their presses. SF is known to have basined some dies in the belief that this would produce better coins on their presses. Based on the coins from SF, they appear to have ground off parts of the design, then tried to cover the mistake by scratching in details. This was also done at SF in 1875 and 1876 on gold $5 and $10.

Paragraph 2 is correct at a superficial level, only.

Paragraph 3 is wrong.

 

Your sources are very dated regardless of a 2012 copyright on one of them.

 

[coinman1794]

Re:Sometimes proof dies were grabbed by mistake for the day, or they were done striking proofs and retired the die to business strikes.

 

No. Proof dies were (after about 1850) carefully polished and kept in separate locked cabinets, precisely so there would be no mix-ups.

 

 

 

 

Then why is it there are so many varieties in many series where a business strike is made with a proof die?

 

mpls, type 2 rev quarters, type 2 rev IKEs, type 2 rev Franklins,....

 

Type 2 halves from 1958 and 1959 and Type B quarters from 1956-1964 were produced using retired proof dies. The various IKE variteies seem to have been produced using Proof and Business Strike hubs, with no evidence of actaul finished proof dies being used.

 

As far as the distinctive PL coins of 1934-1954, I know of several examples, from this period, of specific die varieties that started out fully prooflike and can be collected through each stage of die deterioration, from mirrored to heavy frost. Several prominet ones from 1947-S include 25C FS-501, 25C FS-502, and 10C FS-501. The evidence suggests that these dies were prepared with this unique finish before striking began.