Somebody in the past had the "brilliant" idea to weld to a frame this Ferdinand III Taler from Augsburg, 1642. My dad bought it like this in 1980 (DM 250) - I can only guess that he liked the lionhead shoulder... don't know I went to a coin store and they recommended leaving it as is; however, I am afraid that in time the coin will get even worse than it already is. What would you do ?
thank you very much H8_modern. I agree that it won't improve anything, I just don't want to get things worse, if possible
What do you mean by “getting worse”? I’m not sure mich more could happen to the coin. You might buy an airtite capsule that fits the coin with the additional metal. That will help protect what’s remaining.
I mean the deposits or crystallization (?) that can be seen on the left were the frame is welded to the coin. Does that - the powder or whatever that is - expand to the rest of the coin or through the coin ?
I realized what you mean and am afraid that’s outside my wheelhouse. What I can say is that a soak in pure acetone probably couldn’t hurt to see if it helps.
It looks pretty obvious to me that somebody has already tried to remove the bezel, or frame as you called it, from the coin and gave up after realizing what was happening. Basically that you'd end up with something worse than it was if left alone. As for this - That's caused by moisture. The moisture causes a chemical reaction to between the two disparate metals to occur. Even excessive humidity can do this. The same kind of chemical reaction can been seen when aluminum comes into contact with copper, and moisture is present. In any event it's corrosion. To the best of my knowledge acetone will have no effect on it, will not remove it in other words. And I'm not really sure what would remove it as that would depend on exactly what the metal is that is attached to the coin. If it were me, I'd use a toothbrush, carefully, to brush away what you can. Then store the coin properly so as to reduce the moisture as much as possible. You can do that with silica-gel packs and a sealed container.
