Cleaning A 1928-P Peace Dollar Key Date Help!!

I just did some more research and the average melting point for a silver/copper coin is 879 degrees Celsius (according to a jewelry website)... I think you maybe screwed. "But then why is the front not damaged?" - you may ask. Fires are odd things. Have you ever put a stack of papers in a barrel and tried to burn them? The top pages may burn to a crisp and the page just below could be largely untouched. If the front was face down then it would have been somewhat protected and require a longer exposer time for the heat to transfer... The more I look the more I think the back is melted. IMHO.

"... but it still would be nice to know and it can't hurt at this point to at least find out." - Very true. Like I said in my very first response; I think at this point you can only go up... 99.9% of the time you should not mechanically rub or clean the surface... I used to believe in 100% of the time... till I saw this coin. lol. Seriously though I'd get some kind of solvent soak it for awhile, air dry, if no change soak again, and with a sponge or something soft try rubbing it... it may work, may not, unless you want to contact PCGS or NGC(the links I provided) and see if you can afford a professional restoration; then I think we have come up with the best options.

Again I would stress to NEVER do this under normal circumstances... but if you are merely wanting to find out... then why not.

What do you suppose it will weigh after all the tar is removed?
If not melted, it may be annealed, making it quite soft.
I would try acetone.
Good luck.

Use the Search function on this forum to research the use of acetone. We discuss it with great regularity, and there's a ton of information regarding the safe use. The obverse scratches pretty much killed the coin, in the sense that none of the disadvantages of using acetone (you'll find me listing them frequently in your Search) will apply. This one is a prime candidate for seeing just what acetone is capable of.

For all you find about its' use, use the upper-end timeframe quotes. Every time you sink this coin into a fresh bath, you're going to want to give it overnight at least and probably 24 hours. Do this safely, do not worry about the acetone affecting the coin (it can't), and above all be patient. Acetone should dissolve that coating, if such is possible, but it may take you a week's work to get there. Maybe more.

I would try a long soak in acetone first, but be careful of the fumes and don't get any on your hands, it also might not be strong enough. You might have to use something a little stronger.

Minor updates to my chemistry set...



The cork is drying out and starting to crumble. But as fortune would have it, I am about due for a second bottle and can use the first one for the "used" acetone.
And, after soaking two Morgans, I ran the acetone through a coffee filter before pouring it into the "used" bottle.
Wow! The undissolved matter looked like pepper. Makes me wonder how much stuff gets dissolved.

I guess I should clarify that I wouldn't use gasoline, not primarily because of the fire risk (acetone is quite inflammable too!), but because it contains various impurities & contaminants, & motor-fuel gasoline has various additives in it, which make its use as a solvent less predictable.