Cufflinks by Josef Koppmann The cufflinks are hand made with sterling silver and the bolder opals are set in solid 24carat gold. A hinged bar which is soldered on the back snaps securely into place when worn. Features Primary Material : 18ct gold and sterling silver Fitting Type : hinged bar Dimensions (mm) : 13x23x7 One of a Kind : Yes Metal : 24ct gold and silver Gems : opals Hallmarked : Yes Cleaning InstructionsThe cufflinks are best kept clean by rubbing and brushing them gently under running water with bicarbonate of soda. Do not submerge in water for long periods and do not clean the cufflinks in ultrasonic cleaning systems.