I have the Swagger 27 with rivets in gunmetal, heavy use (daily) for 4 months last year, and the gunmetal is absolutely fine. Except where it has worn shiny on 2 studs where it contacts with the folded down handle and that's rubbed against my body when it's carried crossbody.
BUT I have a new black copper Rogue 25 w/ tea rose in melon, bought Xmas 2017 and the first time I even used the shoulder straps and then checked at the end of the day, a LOT of the black copper had rubbed off on both the rings and the clips. I've since removed the straps out of fear of it wearing. I don't think that's normal but I don't know, I have read that the black copper is just a coating so it's expected to come off?
What a shame! Maybe there’s some bad batches of black copper hardware out there.