Weird Scarborough Faire jewelry question

So I grew up in TX and Scarby was my home faire. Somewhere in the late 90’s I got a coin from there at the booth where you could pick the designs for each side and the guys yelled “Striking!” before dropping the huge heavy thing that imprinted the designs.

They put something on the metal to antique it, and it’s lasted for like 30 fucking years until tonight, when I dropped blueberry jelly of all things on it and the antiquing came off. Now one corner is shiny.

Do any of you happen to know what that stuff was they rubbed on it or something like it I could use to make it all look antiqued again? I’ve lived in New England for a while now, so I can’t just go to Scarby and ask (if that vendor still even exists).