Very nice bracelet find, mermaid! I see "Made in France," also. Possibly Renaissance Revival? They say a dab of ketchup or lemon juice may remove the greenies, but it also removes the plate and leaves a dull base metal color. I don't think there's much else you can do once the dreaded verdigris sets in 
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I've always assumed that when you find dull base metal under verdigris, it's not the fault of the vinegar, but that either the verdigris ate the plating or the plating was damaged in the first place.
I agree with Blue. It isn't the vinegar that damages the plating it is the verdigris that has eaten away the plating.
This is a pretty piece. I can't see the cameo well enough to tell for sure, but if it's not shell then it is possibly soapstone.
