Here is a 1787 George III shilling. What's interesting about it is that, once upon a time, it was gold-plated (?) and counter-stricken "M.A.S."
Has anyone seen similar coins? what's what all about?
It originally was silver, 'til someone painted? it over. Generally, if your coin was in very fine shape, it would be worth only around $25. Could be more with the counterstamp...or less.
The coin is not painted. Rather, it looks like somebody plated it with a gold layer to make it look like a gold coin and as the wear of the coin stripped away the gold at the "normal wear spots", the silver inside came out again.
It could have been plated many years after the coin circulated, so was already a worn coin. And then it circulated again wearing off some of the plating. Usually when a coin is countermarked it's the mark that holds the significance, and if it's a genuine coin, then obviously it had value too. To gold plate it seems odd, but there's no arguing because it's pretty clear that is what's going on. It certainly would not pass as a counterfeit gold, so someone definitely had a method for their madness. Things like this you can do the diagnostics to know what it is, but that doesn't necessarily tell you what you have.... in the sense of why it was done. Also, with the letters spaced that much it's probably three separate punches and not a single stamp.