Good points, Russ, & fun insight into the big world of fashion jewelry components!
I'm not knowledgeable about plating issues, but sometimes it can be a function of the alloy used to plate, too. Years ago I bought cheap silver--plated headpins from a company I won't name (NOT R&T!!)

and the plating cracked, just as you said, when I made loops and bends. My guy in Providence RI, after looking at my sad collection of headpins that didn't work, said it had something to do with too much.....chrome???...in the plating. Made the plating brittle rather than the same malleability as the brass.
It's kinda cool to see how much planning and knowledge goes into something as the ubiquitous head pin!
