Helen, (without the benefit of a photo) the intials, FM are the maker's mark and I would say this ring is not an antique gold ring. Why do I not think it is not an antique gold ring?
In 1978, the karat mark followed by a P was introduced so that the manufacturer could make sure that a piece was PLUMB gold. If the ring is stamped 10KP, it is guaranteed to be NOT LESS less than 10k.
