Gold identification

Hello all; I am an amateur smith who gets about an hour long seminar
each morning from all of you fine people on this list. Don’t ever
stop, I would be lost. Today I was handed a couple of rings to repair
on which I found markings I am not familiar with. One ring is marked
14kPC, and the other is marked 10kGTR. Do these suffix designations
have anything to do with the formula of the gold? If so, what should
I use to solder them? Next question, if you’ll indulge me, can I
solder 10k gold to 14k? And what solder should I use? Thanks in
advance for your patience and your