Old-school Dura Ace chainring markings: 'TO', 'SR', 'SS', 'YG'
So, I've got a pile of NOS early Dura Ace chainrings, presumably from the 1970s or early 1980s (?).
Most are packaged like so, some are without packaging:
Most are simply marked 'Shimano' + '[tooth count]'.
However, several have other letter-markings next to the 'Shimano' stamping: four different markings I've found are 'TO', 'SR', 'SS' and 'YG'.
Does anybody know what these designations mean? I've tried searching for info, and not much luck.
'SS' = track, maybe? I know the Shimano track cogs are currently designated as SS-7600, etc., for 'single sprocket'.
Seems vaguely possible, but not so sure about that at all. And what about the others?
These are the markings in question:
'YG' (and the 'circle-S', which I've not seen elsewhere):
Any thoughts? Little help? Thanks!
Last edited by mikemowbz; 08-29-12 at 12:13 PM.