Peter: I'll see if I can get some more, but if not I could snap a piece off one for you as I managed to 'open' a ring without shattering the whole thing recently They're flat rings, presumably cut from a sheet 0.5mm thick, outside diameter ~13cm, inside diameter ~10cm. They were something special, but the only idea I've had is they may have been the wear surface of a thrust bearing. I'll try contacting you through the email address you post with for your address details.
Scrim