Onyx ring 18 kt buying gold electroplate rectangle stone raised setting mens pinkie ring unisex ring size 8 8 1/2 vintage ring

Vintage ring stamped buying 18kt electroplate. Beautiful raised setting. I haven't had the stone tested but I think it is onyx, a very black opaque rectangle cut stone. This ring is in excellent vintage condition. Would make a great pinkie ring. See photo with ring sizer for size.
Measurements
Band is almost 1/4 inch wide in the back and 3/8 inch wide at stone setting
Stone is 3/8 inch tall and 1/2 inch wide