Factory original key tags, and a truly amazing find!

Gentlemen: Does anyone remember that little aluminum ring that originally came with your car's keys when the car was delivered new? It was about as large as a quarter and had a six digit code ("key code" according to the owner's manual) stamped in it. Does anyone still own their original? The owner's manual says to record the number, then destroy the tag. Not sure why you wouldn't just keep the tag. Apparently, the code on the tag could be used to reproduce your keys. Any photos of this tag out there? Does anyone repop these? Thanks!