soviet union gold and amber cufflinks

hi all these are my soviet union cufflinks 9 to 12 carat gold had them tested at 2 jewellery shops. they also have a amber peice. stamped with the number 3 backwards R and normal K. the stamp above has a P and a star with sickle and hammer and 875, what ive read about these pieces 875 are normally silver but these are definetly gold as ive had them tested twice at 2 seperate jewellers. the jewellers could only say they were gold and amber but know nothing else about them any info about them at all would be great thanks.