1625 Swedish Silver Bug.

Although this coin bears the name of the Swedish queen Christina, it has been issued in Riga (Livonia), during the Swedish occupation. It is in Krause as Livonia, solidus KM#21. The year is probably 1653.

I am afraid I can't help you in getting the green stuff off. Be careful with this little chap!

Here's the old thread about this coin.

While Krause lists it as silver, the fact that it's turned red and green is a good indication it's actually made of billon, or low grade silver alloyed with copper, lead, or whatever else was lying around the mint that day. It was not designed to last for several centuries, and rarely looks good. Black and crumbly is the normal colour for it. There will be enough copper in it for it to turn green under the right (or I should say "wrong") conditions. However, this green patch doesn't look like typical "bronze disease". It's probably stable and un-contagious, and it certainly won't hurt your silver coins.


Acetone won't hurt it. It's also unlikely to do anything to this kind of red-green deposit.


Definitely no vinegar or other acids; it's too thin and the alloy quality is too poor. Personally, I would leave it as-is; anything you do to it that's strong enough to remove the green goo is likely to have adverse effects on the rest of the coin.

Nice coin! I have an Livonia Solidus from 1657, and off-center strike and not as nice as yours: