So recently, I was examining a mint set of mine from 1970 and I noticed on the Philly coins a sorta swirling greenish pattern to it. At first, I thought it was PVC residue but it is totally flat and on the coin. When I tilt the coin I see a nice gold/pink toning to the coin but at most angles it is an ugly greenish swirling pattern. I took photos but of course I don't have them with me at work...I can post later if needed. Based on photos I have seen, I don't think it is PVC related (it's totally flat and doesn't appear growth like) but I pulled the quarter out (because I want it for a book) and gave it a good acetone soak...three baths over a day and nothing changed. But...this situation made me wonder. Do older (not that 1970 is old for any of you "not older" folks here) mint set plastics contain PVC? I did an internet search and I found a couple other posts on other forums that hinted that US sets never have but some world mints have. I tried to do a search here but couldn't come up with a specific enough search to give me the results I was looking for. So, I thought I would ask. My inkling is that they do not as we don't see PVC damaged mint sets from the 70s left and right...but I thought I would ask just to be certain.
Here is a few I photo'd from some 1970 U.C. sets. All of them were stored incorrectly. Is this what you are seeing?
1970 sets came packaged in cellophane. It probably sprung leaks over the years allowing exposure to the atmosphere
It's a little like that but not nearly as bad. The funny thing is, on the obverse there is really lovely toning under the right light but under most light its ugly. That's what I thought. Thanks Doug.
In my opinion I would guess that the sets were exposed to extreme heat. Causing them to sweat. I am not really positive that is the reason. Just my best guess. These sets were bought by a collector in Dallas Texas, and sold to me in the original mint packaging. Either way I would say it is a form of environmental damage.
Back in the 60's and 70's they didn't have minivans or SUV's. At the end of a show the dealer would pack all the coins into the UNAIRCONDITIONED trunk of their full sized sedans, and then go driving off in the summer heat. You know how hot it can get in you car after you leave it parked in the sun all day. Well that was the baking the coins got for hours traveling between every show. Those trunks probably got to 140 or 150 degrees or more. PLUS any heat from the muffler, not to mention exhaust leaks.
So, am I right? have you seen this look before? I would imagine that the sets would also tend to sweat some. and the reason that the damage is swirling around on the cents.
They would only "sweat" if and when they suddenly went from a very hot place to a very cool place. The only thing that can cause a coin to "sweat" is the sudden and drastic change in temperature. If allowed to warm up slowly, or cool down slowly - it never happens. But under the right conditions, yeah it can happen.
These sets have something funky on the inside of the packaging that will destroy the coins if they are left in long enough. As a rule coins should be removed and soaked in acetone or 91% alcohol. Most of the coins are already damaged.
No doubt acetone, xylene. Nothing has even touched the surfaces. The coins are forever damaged. I have only hoped that they would tone over. But, that hasn't happened either.
Mint set packaging is four layers and the layers touching the coins is soft "plastic". The coins will tarnish if left in this packaging. After they begin tarnishing many of them can be saved with a soak. However, in time there is nothing that can be done. I'd guess most mint sets are already damaged and more than 75% of some of these can not be saved. '68-P pennies are the worst with virtually all of them in the plastic being severely damaged and those that were removed are usually carbon spotted. It doesn't really seem to matter because no one is collecting moderns. The few who do don't mind tarnish and carbon spots. After all these years there might never be any real demand. But if everyone with bad '68 cents tried to replace them with good ones there would be a big surprise. A lot of "common" high mintage moderns from the US and world are scarcer than most of the old "key dates" in chBU. In all these years I've seen only a single Gem '82 quarter and a single Gem '84-P cent with good surfaces. Gem '69 quarters were tough in 1969, nobody saved them, and now most of the mint set coins have been destroyed by the packaging. I've never found anything that can restore tarnished mint set coins. The tarnish can be stripped off with good ammonia but the coin looks cleaned most of the time.
I have found that the polyfilm provides good protection if you don't jam the coins into boxes or put a heavy weight on the coins so that the rims cut into the holdes. Also you don't store your coins in your attic or garage. Here in Florida, I've seen more than my share of baked coins. You can even screw up gold pieces if you bake them in Florida. I've seen them.
