Antique gold, onyx, diamond ring.

by Sam Maves
(Kalispell,MT,USA)

Have traced my ring to 1950s in family photos. Men's ring, nice rectangular onyx, about .500X.625, diamond set in platinum in center. Marked inside band ")H(" and "10K" the parentheses and the 'H' are linked together through the crossbar in the H. Any help would be appreciated. I took this to a Jeweler I have personally known for over 35 years and it is real, but no idea on the H mark inside.