Vintage Mexican Mexico 1950's modernist Large purple stone sterling silver ring

This stunner is a collectable vintage piece. Made in Mexico circa 1950's. Marked 925 Mexico with the makers intials J S and their eagle 93 stamp. The stone is a man made Alexandrite color changing stone. The colors range from dark to light purple, bright pink and dark blue depending on the light. It was difficult to capture the different colors in a photo especially the blue. For some reason I couldn't get it to show up well. Considering the age, this ring is in EXCELLENT condition. The stone has only minor imperfections on the surface and the silver has the normal scratches and signs of wear for a ring this age. No dents in the silver. There is on Prong that is missing the top piece(which goes over the stone). I purchased it this way many years ago and never had it fixed, and I never had issues with the stone being loose. Size 5 1/2 Please feel free to ask questions. Reasonable offers considered. Thanks for looking!