Why do proof coins and business coins tone so differently?
Danye West
Posts: 193 ✭✭✭
I can never imagine buying a MS nickel like this for just a handful of bills. 
I could make a birth year registry set out of pocket change.
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Assuming we are writing about naturally toned coins; I would suggest initial packaging, subsequent storage conditions and the presence of flow lines (MS) vs. reduced flow lines (PR) on the surfaces of coins.
In honor of the memory of Cpl. Michael E. Thompson
Surface finish would most likely be the reason.
During the Barber coin era (and possibly decades earlier and later) the US proofs shipped out by the Mint had the coins individually wrapped in heavy paper. This wasn't much different than storing them in standard 2X2 paper envelopes. If left in those long enough they could tone into deeper mottled browns and then to deep blue/purple/heading to black. If rescued early enough you could get majestic colors. Any business strikes saved during those periods wouldn't have the same sulfur-laden environment to tone in.
Actually, pretty toned proofs 1950-64 are way up in price especially the nice ones.
rainbowroosie April 1, 2003
I had nickel that was toned like this in a 1962 Proof set. I viewed it as a cull because toned modern Proofs were viewed as "problem coins" in those days. I decided to sell the set as Proof singles. When I cut the nickel out of its window, a sharp glue smell walfted out of the spot. The color had been induced by a less than perfect flat pack seal.
The mint package storage devices are far different for Proof and business strike coins.
Good info on OGP NT toning.
A toned proof Jefferson set would be quite the looker.
From what I have seen, the striking gives the coin a different finish, and possibly more. For toned coins in proof/MS that I have seen, I believe that to be more of a difference than any outside influence.
In other words, packaging doesn't give 2 equal coins, one being a proof and one being a business strike, the only difference. Rather, put the 2 coins into the same environment, at the same time, and I believe they will tone differently and that is due to the strike.
Proof SAE vs MS SAE.
Proof nickel (non-silver) of a certain year vs mint state nickel (non-silver) of the same year.
I've seen this with the SAEs. I have looked at others as the SAEs are much quicker to tone naturally due to their "pure" silver content.
Some may be able to look at silver Washington quarters/Roosevelt dimes that are in storage conditions where both the proof and mint state versions are in an album or something.
I've been told I tolerate fools poorly...that may explain things if I have a problem with you. Current ebay items - Nothing at the moment
Certainly the metal surfaces are different between MS and PR.... I have been away from my metallurgical studies for too long to properly state why they tarnish differently... I am sure it has to something to do with the molecular structure resulting from the process.... I should look this up I guess...Cheers, RickO
I agree with this.
If you examine both coins under a very high magnification, you'll probably find the proof is relatively smooth (a mirror finish), where the uncirc is pitted (to make a more matte finish). If I were to guess, the matte finished coin has more than twice the exposed surface area than the proof, so the way the metal oxidizes would be different.
Since the proof is smoother the oxidation would be more consistent across the fields so you get that continuous electric toning.
(Anyone have access to a SEM? It would be interesting to see the actual surface of proof, matte and heavily frosted finishes, as well as what the oxidation actually looks like on a toned coin...)
Then if comes down the the different chemicals in the environment to help the color along...
Perhaps the way the surfaces of the planchets are cleaned, or not cleaned, prior to striking and the residues left on them, or not left on them, affects the ways the coins later tone?
TD
Thank you all for the information!