Well, here's another bit of bicycling history! Another rear derailleur... this time from the French maker, Simplex. I'm not an expert on such things, and apparently even experts have a hard time identifying specific models and years of Simplex derailleurs. At least that's what the book The Dancing Chain (http://www.thedancingchain.com/) says. In case you've never seen it, that book is an amazing history, primarily of the derailleur bicycle, but also of bicycles in general. Some of you may remember Frank Berto from older issues of Bicycling! magazine (back in the late 70s and early 80s, the good ol' days)... he's the lead author of the book, and it's really an excellent text.
Anyway, best guess is this is a late 50s Simplex, based on the plastic pulley. As you can see, it's missing one pulley and the hardware to mount it. A shame, because otherwise it appears to be in excellent shape. Unlike the modern parallelogram derailleur, this one operates on a push/pull rod of sorts, where there's a large coil spring that returns the pulleys to the innermost cog, and a cable connected to a "pull chain" (similar to that on the the old Sturmey Archer 3 speed hub gears) pulls against the spring to move to the outer cogs. I'm guessing when this was made, we were shifting across 3 or maybe 4 cogs. Seems strange when today we have recently seen the introduction of an 11 cog rear cluster, but 3 or 4 was the norm back in the day. The back side of the pulley cage is stamped "4 vit. chaine 238", which I believe means "4 speeds (vitesses)". Not sure what the 238 means. A model number? Maybe.
A fun thing to have, I have to admit. The oldest derailleur I've ever owned, and definitely the least like a modern one. I really like the black main pivot with gold lettering... very snazzy looking! Most Americans, if they know Simplex at all, probably associate them with their Prestige derailleur from the 60s and 70s, which came on any number of bikes in those days. It's singular feature was that it was made almost entirely from delrin, a low friction plastic, very high tech in its day, I suppose. You'll find lots of discussion online about the Prestige, I'd bet, both pro and con. I've owned a couple of bikes with them, and they shift well, but seem really flimsy. And the front derailleur mountings eventually crack with age, pretty consistently in my experience.
If anyone knows more about this derailleur, please let me know. And no, I'm not interested in parting with it. But if you have a source for the missing hardware, let me know!