Why is my coin shiny? Why is our coins shiny? :-) 0

[ZudenSterne]

I am fairly new here, but I have already seen LOTS of the of posts asking if a 96P penny is a proof coin or if some older nicer-than-average coin is a proof with no mint mark etc. because it was shiny.  I understand where people are coming from, but generally speaking, actual proof sets look like mirrors and have an S.  They also shouldn't be in circulation in the first place - but can be found there occasionally if someone cracked a set and spent it.  This is rare, but I have found one before.

However, there are other reasons for coins to be shiny than being a proof, especially when not an 'S' mint mark.  Can someone help me/the world understand likely other reasons for extra 'shininess' we might encounter?  Maybe this can help get less questions about impossibly rare 'wrong mint mark proofs'...

For example...

1. Being uncirculated. Does every coin come off the press Brilliant Uncirculated?  Or is there something that makes some shinier than others?

The coins attached were both found in a bank roll and are in good shape for pocket change.  They have a similar number of minor nicks/scratches, but one has a frosted/clouded finish like almost every nice pocket change coin in collection books.  However, the other is one of 5-6 I have found that have a mirrory proof-like finish, but is still a 'P' or 'D'.  Did I just catch them sooner in their life than others or is there another reason?

2.  I also saw that the National Park Quarters are/were sold in collector sets of 6 coins. They aren't 'proof' sets, but they are collector sets with a D mint mark and a nice finish.  Have I really found a half dozen coins from broken sets spent as change?  Seems unlikely, but maybe.

What other reasons do some have mirrory finishes that stand out from the rest?

Thanks in advance!

- Long time passive collector, but noob serious collector

[Greenstang]

Often coins are polished after they leave the Mint, especially the State and Territory series as a means of selling them as souvenirs. They were also at times plated in gold and sold to the unsuspecting public.

[Conder101]

When the dies are created, after hardening and tempering, they will usually have an oxide layer on the surfaces.  They are typically cleaned and polished to remove this surface.  This polishing can sometime result in surfaces on a business strike die that a similar to the highly polished surfaces of a proof die.  When this happens early strikes from this brand new die will have "prooflike" fields until the die begins to wear a little bit and the coins start to take on the cartwhel luster we are familiar with on MS coins.

[VKurtB]

On 9/29/2019 at 3:11 AM, Conder101 said:

When the dies are created, after hardening and tempering, they will usually have an oxide layer on the surfaces.  They are typically cleaned and polished to remove this surface.  This polishing can sometime result in surfaces on a business strike die that a similar to the highly polished surfaces of a proof die.  When this happens early strikes from this brand new die will have "prooflike" fields until the die begins to wear a little bit and the coins start to take on the cartwhel luster we are familiar with on MS coins.

I've found that the so-called "circulation strike" S mint quarters have a higher than normal propensity to be "prooflike". They really are quite magnificent, right out of the roll and/or bag.

[Conder101]

Not too surprising with the low mintage the entire coinage of each COULD be done with just two die pairs.  But I would bet that in order to do them faster they use more presses and die pairs.  If they do that then the number of coins struck from each die pairs would be much lower and the overall proportion of PL coins would be much higher.  So your observations are very reasonable.

Edited October 1, 2019 by Conder101

[ZudenSterne]

Great point.

[ZudenSterne]

This is the plausible answer that I was looking for.  Early business strikes looking 'proof-like' makes sense and the ones I am talking about are just occasional finds from bank rolls and do not look plated or polished.  Thank you for the info!

[VKurtB]

The other factor at work here is that ALL the S-mint America The Beautiful quarters, whether proof or not, have been struck on a press that was designed AND used for striking proof coins. The so-called circulation strikes are merely struck once, rather than twice, and the dies are not specially polished. At San Francisco, all quarters, proof or not, are struck on an older slower press that strikes coins vertically, downward, and not side-to-side horizontally, as they are in the Philly and Denver high production presses. I don't yet know how they're doing the ones at West Point, but they are not as uniformly gorgeous as the San Fran ones are.