Well, here's one you don't see every day!
This is a Campagnolo Gran Turismo rear derailleur, from the early 70s. Bike folk know Campagnolo (Campy for short, unless your British, then it's Campag) mostly for their fine racing derailleurs and other components. This one was intended for touring, and was designed with a wide range of sprocket (back of the bike) and chain ring (front) sizes in mind. And it's nothing like their famous Record series racing derailleurs in any way. They were light, pretty, elegant even. This one, not so much. It weighs in at nearly a pound, and it's made of stamped steel, with a lot of seemingly uneccessary bulk to it. I've always thought it had a vaguely "Klingon" look to it, with the pointy/swoopy thing going on at the front/top of the pulley cage.
Until a few years ago, I had only seen one briefly, in passing, on a housemate's older Schwinn. Then my buddy Geoff at the Community Cycling Center found a Schwinn Sports Tourer and bought it. I don't recall what he ultimately did with the bike, but he decided right away he didn't want the derailleur, and I asked for it as a curiousity. Geoff was more than happy to be rid of it. I've kept it around as a little piece of history and a paperweight, and don't expect to ever put it on a bike. I'm all for period correctness, as long as it doesn't mean using a really bad piece of equipment, and from what I've heard, that's what the GT is. I've heard more than one person derisively refer to it as the "Gran Trashmo", and the esteemed bike technology historian (yes, there is such a thing) Frank Berto wrote "The Gran Turismo was arguably the worst rear derailleur to carry Campagnolo's name. I blew the whistle on it. The Gran Turismo was my litmus test for bicycle writers. If a writer praised it, it meant that he had never pedaled it or he was lying..." (The Dancing Chain, Van der Plas Pub., copyright 2000).
The funny thing is, my 1973 Schwinn Paramount P-15 (http://spokesofawheel.blogspot.com/2007/08/my-new-bike.html) has its original "Schwinn-Approved" rear derailleur, a re-badged Shimano Crane GS, which was new to the Paramount that year. The '71 and '72 models actually came with a Gran Turismo instead! And that's why I'm glad I have a '73! If I had an earlier one, I'd have to decide between "correct" and "good"... and the Crane is both of those things, as well as prettier than the GT.