Vintage antique sterling silver light blue cats like glass cabochon ? Ring Victorian looking signed D. Adjustable approximately 7-8

Vintage antique sterling silver light blue cats like glass cabochon ?

This ring is really nice, it is an unusual make, it is adjustable by one side sliding into the top of the rain and back out so it adjusts from approximately 7 to size 8 please see photos as the band is slightly out of shape but it does not affect the feel of the ring at all. I am not sure if this is glass cat’s-eye or a light blue gemstone it is slightly mottled at the top which you cannot see unless you look up very close.

This ring is signed Sterling and then the letter D in cursive.