I came across this in a local shop yesterday. It looks to be a variation of the 3rd generation Campagnolo GS rear derailleur, with a few odd differences.
- Derailleur body only stamped "Campagnolo" No model name, no "record", "gran sport" etc.
- Reverse of derailleur body where max cog info is, is complete smooth and devoid of markings, it is also un-plated, but polished steel.
- There are no markings on the derailleur cage
- Two different types of steel pulleys. Bottom is "round" style GS, top is early toothed NR
- Upper and lower pivots are bare brass that does not look to have ever been plated
- "stop" screw for cage threads in from the bottom and not the top
There are a few other minor differences here and there.
I'm wondering if this is some sort of transitional derailleur between 'gran sport' and 'record' or perhaps something completely different.
Pics can be seen here:
Though listmembers may be interested in seeing this.
San Francisco, CA