Can someone please offer any info on a few drilled rings I came across. These are nicely finished silver anodized rings, factory drilled (a la Eddy) and are simply inscribed with "S-54" (or whatever the number of teeth). No overshift pins and no other manufacturers ID. Perhaps Sugino?... Possibly late 70s?... 80s?
I know I've seen these before but I never thought to inquire about their age or original source.
Thanks!
Bob Hanson, Albuquerque, NM, USA