Vintage Goldstone & Sterling Silver Ring - Signed

This sterling silver, and what I believe is goldstone, modernist ring is stamped G.C.01 925. Based on my researched, it is likely from one of Mexico's most sought after designers, Pepe Cerroblanco. He studied jewelry design in Italy. All his jewelry is handcrafted of gold or sterling silver. Apparently his early work is difficult to find. The ring is approximately a size 6 3/4 - 7. The head of the ring is approximately 1" x 1/2", and is in excellent condition with no sign of damage or repair. It has some tarnish/patina. See pictures.