OLDER 14K CAN BLACKEN OR "TARNISH" IF YOU WANT - IF THE OTHER PART - (THE METAL USED IN PLACE OF THE GOLD= THE OTHER 10K IF YOU WILL)
IS SILVER - I HAVE FOUND OLDER GOLD MORE THAN A FEW TIMES WHERE SILVER WAS ADDED TO THE GOLD INSTEAD OF COPPER OR NICKLE OR WHATEVER
AND IT WILL TURN DARK A FEW DAYS AFTER I SHINE IT UP - MINE ARE NOT PLATED - THEY TEST POSITIVE AS GOLD
I FOUND AN OLDER 10K CLASS RING THIS YEAR THAT SHINES UP NICE BUT IF LEFT ALONE IN DISPLAY CASE IT WILL SLOWLY DARKEN
SO I JUST LEAVE IT ALONE NOW- IF I EVENTUALLY FIND THE OWNER I WILL SHINE IT UP FOR THEM -- I BELEIVE COMPANIES BACK THEN
THAT USED SILVER AS AS AN ALLOY WERE NOT AWARE THAT THIS WOULD HAPPEN - IF YOU NOTICE THEY DONT USE IT ANYMORE