I just received a somewhat unusual (to me anyway) Campy NR rear derailleur. The distinguishing characteristics are four:
1. No Patent or date marking in the usual spot or anywhere else
2. Nothing written on the back of the body, e.g., no Campagnolo
3. The most unusual part is the way the body tension spring in held in place. Rather than the typical situation where the spring fits on a bolt which threads on to a mount on the upper body this one has the spring held in place by one of the pins which also holds the front abd rear body plates together. The bolt mounting piece is not in the forging, nor has it been filed off. Also the spring doesn't have the round loop on the end that touches the inside of the body, it's just a straight piece slightly curved up at the end.
4. The pins that hold the body together are open one one end rather than rounded ones on both sides.
Everything else looks like a typical 70s rear NR derailleur.
Sound familiar to anyone?