I've torn down my Peter Mooney bike for refurbishing this winter, cleaning and polishing all the components. The earlier Campagnolo derailleurs had a certain sculptural feel to them, as if they had to be beautiful as well as functional.
This particular rear derailleur is one of those things that theorically doesn't exist. Campy boxes are quite nice. There people who buy, sell and collect the boxes. Weird. I bought this a few years ago from a reputable European dealer. The box this came in was a classic blue Campagnolo box, labeled, to the best of my recollection, simply as "Rally Derailleur".
The rollers have been replaced by sealed bearing rollers and the Campagnolo lettering buffed off (both of which, the purests would kill me for). The Rally derailleurs were designed to wrap a lot of chain for triple chainring touring bikes. As I said, theoretically Rally derailleurs had been discontinued by the late 80s. The closest thing I have found to this in the Campagnolo catalogs is the 1990 Euclid mountain bike derailleur, with only a slight variance in the bottom roller guard.
That's all, folks. More than you wanted to know.
Chuck Schmidt has advised me that it is indeed a late 1980's third generation Campagnolo Rally.