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How does the mint apply a satin finish? How do you detect porosity?

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You might get more replies if you make your thread title a lot less vague and more to the point.

 

For example: "How does the mint apply a satin finish to coins? How do you detect porosity?"

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I think that if you click on "edit" at the bottom right of your post, you can change the thread title and/or your post.

 

If you want to see porosity, a good place to start is by looking at images of early copper coinage, such as 1793 Large Cents and Half Cents. Many of them are porous. I am still looking for a good answer to your other question - hopefully Mr. RWB will chime in.

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Hope that helps :)

The “satin finish” was created by sandblasting the faces of the dies and burnishing coin blanks before striking. The resulting coins have a frosted appearance that is distinguishable from regular business strikes.

 

 

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To add to what "rider" said, when the Mint decided to produce the Uncirculated Mint Sets with a satin finish, they experimented blasting the dies with a combination of sand and glass beads of varying sizes until the right "mix" was found.

 

Chris

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The dies for "satin finish" mint set coins made between 2005 and 2010 were chromium plated. Dies for mint set coins have long gotten a little extra attention sometimes but these dies were specially prepared for the mint sets. The mint was trying to improve quality in response to customer demand but many collectors prefer premium examples of circulating coinage to coins that are distinct from circulating coinage. Ironically this is going to make almost all circulation issues for these years scarce in high grade.

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The satin finish question has a more complex answer that one might expect. I'll mention only the pre-1965, since in the 1980s the mint started monkeying around with the definition.

 

A "satin" proof was one made on a medal press from dies that had not been polished or altered in any way. The coin surfaces resemble smooth, non-mirror metal free of flow lines that create luster.

 

A "sandblast" proof was a satin proof that had been lightly sandblasted at the mint. The work was done individually on each coin.

 

The two above applied only to gold and silver between 1907 and 1922, plus some classic commemoratives, and some early 1936 proofs.

 

A "matte" proof is made by sandblasting the soft dies, then hardening the dies and striking coins on a medal press. This applies only to Lincoln cents 1909-1916 and Buffalo nickels 1913-1916.

 

I hope this helps. Look in the "Renaissance of American Coinage" books for more extensive descriptions and photos.

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The dies for "satin finish" mint set coins made between 2005 and 2010 were chromium plated. Dies for mint set coins have long gotten a little extra attention sometimes but these dies were specially prepared for the mint sets. The mint was trying to improve quality in response to customer demand but many collectors prefer premium examples of circulating coinage to coins that are distinct from circulating coinage. Ironically this is going to make almost all circulation issues for these years scarce in high grade.

 

Despite being chromium-plated, the Mint found that the dies did not last as long as they had hoped. (It's probably why they discontinued the program.) If you examine some of the business strikes that were produced during the same period, you will find that they were struck using the satin finish dies that had deteriorated. Of course, since these were ordinary coins intended for circulation, the quality was of little concern to the Mint. I've been fortunate to be able to get a number of MS68's from searching bags of business strikes, but you're right, it is harder to find them in the higher grades.

 

Chris

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Chromium plated dies were used as early as 1937 for proofs and 1943 for zinc coated steel cents. Having a chromium surface does not equate to a modern "satin" finish....the surface can be whatever is desired.

 

Chromium was used for its durability, hardness and ability to release better than a steel die surface.

 

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