CAST, an onyx, white agate, chrysoprase and diamond 'Flip Milan' ring

CAST, an onyx, white agate, chrysoprase and diamond 'Flip Milan' ring, the central reversable section with a chrysoprase cabochon to one side and pavé-set with diamonds to the other, within a reversable frame set with onyx and white agate, to a yellow gold mount accented with diamonds to the shoulders, signed CAST No.54, stamped 750, size L 1/2, case by CAST