12k

Stumped on 'G' Stamp! 1950's Atomic style pin stamped "12k G" ?? I am familiar with 12k GF (Gold Fill) but I have never seen just a 'G' (maybe a 'C'?) :icon_scratch: ...The stamp is not cut off either as if the 'F' didn't make it. Any input is welcome! Thanks so much! P.S. Complete stamp...