If it was solid Gold it would definitely have a marking.Sorry wrong wording it didn't actually snap it bent and broke after a bit of muscling... and that grey colour is paint and cement on my basement floor from the "smacking"... the only marking is the G on the watch clasp
Do you have an used AP solution?
If so, you could run it for a few days.
If it is brass or bronze that would be apparent after some time when the copper get exposed.