1973d Cent 1 1

[cobymordet]

I noticed on two bumps on the REV and would imagine it to be copper plating blah blah from a Zinc. . . but 1973 is a bit early for that.  The coin is in decent shape with no significant impact damage.  Any ideas what caused this?

 

[Fenntucky Mike]

Die defect, damage, or wear/erosion of some kind. I don't have a specific answer other than there are a lot of possibilities. Maybe a small chip that has rounded from wear/use? If this was a variety of some sort they would probably be used as die markers or for identifying die state.

Are you talking about the raised dot next to "ONE" and below the steps of the memorial? 

[cobymordet]

On 1/4/2024 at 4:30 PM, Fenntucky Mike said:

Are you talking about the raised dot next to "ONE" and below the steps of the memorial? 

No, One bump is at the far left base of the memorial, between U(nited) and O(ne)

The second bump cuts NW to SE diagonally through the far left 4 pillars.  It isn't easy to photograph what the eye can see

[J P M]

It looks like there was something wrong with the die. You can see lots of polish lines in those areas

[EagleRJO]

On 1/4/2024 at 5:01 PM, cobymordet said:

... imagine it to be copper plating blah blah from a Zinc. . . but 1973 is a bit early for that

Yea, the plated zinc cents started to be used in 1982, so that 1973 cent would be 95% copper.

The "bumps" are likely minor die defects like chips as noted.

[Greenstang]

Hard to tell from photos but they could also be Occulated Gas Bubbles.

[cobymordet]

Winner Winner Chicken dinner?!?  I dunno, but void of value gives way to a cool new term "occluded gas bubble"  It is always fun to learn a new term, so I like it.  I won't be popping these zits to prove otherwise.  Thanks all for the information!

From: "coinworld.com"

Occluded gas bubbles

The only remaining possibility is that these are occluded gas bubbles. In this rare planchet defect, heat generated by the strike causes a pocket of gas to form and expand below the surface of the coin.

An “occluded” gas bubble is simply one whose roof has remained intact instead of rupturing from the internal pressure. If the roof is of sufficient thickness, it could conceivably resist pressure from a toothpick.

The occluded gas bubble hypothesis is supported by a microscopic surface texture that is identical to the surrounding field. Even microscopic die flow lines continue across the two bulges without interruption. This supports the idea that the die face was intact and undisturbed when the coin was struck.

Occluded gas bubbles are restricted to solid-alloy coins and should be distinguished from plating blisters that form in copper-plated zinc cents. Blistered plating occurs when there is a poor bond between the copper plating and the zinc core.

 

[VKurtB]

I occasionally suffer from occluded gas bubbles. Or rather people in the same room do, when they cease to be occluded. 

[Henri Charriere]

🐓:  Me thinketh any discussion regarding bumps should be referred to a local authority for deliberation, Master Bumpologist @Mike Meenderink .  🤣

[R__Rash]

For those who genuinely care for others and gassy s-cents.

Edited January 5 by R__Rash

[Sandon]

    I think that the ghostly, raised areas on the reverse of this 1973-D Lincoln cent are most likely a phenomenon seen on coins struck from worn dies known as "progressive indirect die transfer".  See https://www.error-ref.com/?s=progressive+transfer, which describes this phenomenon, using the acronym "PIDT" as follows:

"The cause of PIDT is straightforward. When the hammer die (obverse die) strikes the planchet, the force of the strike is transferred into and through the planchet and onto the opposing die (reverse or anvil die). Since the dies are slightly convex, the strongest force felt on the planchet is in the center of that planchet. However, in the case of the Lincoln cent, the center of the obverse die is incuse, so the area on the obverse die that experiences the first and strongest force is the field area immediately adjacent to Lincoln’s bust. Each strike transmits part of the force onto the opposing die. The area that transfers the most force onto the reverse die is the outline of Lincoln’s bust. This transferred force produces uneven metal flow in the reverse die, gradually creating a “ghost” image of Lincoln.

"Since coins that are in a Late Die State (LDS) develop this trait, it is considered a form of die deterioration."

    The bulge within the Lincoln Memorial on the 1973-D cent appears to be the outline of Lincoln's bust from the other side of the coin. The photos shown on the linked error-ref.com page show coins with similar, reversed ghost-like images of the outlines of the design from the other side of the coin.

[Fenntucky Mike]

On 1/4/2024 at 5:41 PM, cobymordet said:

No, One bump is at the far left base of the memorial, between U(nited) and O(ne)

The second bump cuts NW to SE diagonally through the far left 4 pillars.  It isn't easy to photograph what the eye can see

Ah I see now, thanks.

They look more like occluded gas bubbles to me, as opposed to progressive indirect die transfer, but either is possible. 

 

Edited January 5 by Fenntucky Mike

[Coinbuf]

Here is an overlay from Mad die clashes so you can see where the elements from each side can impact the other in the cases of clashing and/or indirect die transfer.   As you can see there is nothing around the corner of the memorial that would cause what you are seeing on your coin.   And the obv bust is not in the correct place for the anomaly under the columns, that largely rules out indirect die transfer or a clash.   So, either an issue with the die (die gouge or large scrape) or occluded gas bubbles; possibly even both; are the likely culprit.