Hi all:

My current ride is a 1982 Grand Jubilee, a bike I like a lot. It's pretty much all original. It came stock with Simplex SX610 derailleurs, which have always been, well, ok. But lately I'm finding the rear derailleur is going out of adjustment pretty frequently and I have a lot of trouble keeping it dialed in: either it won't want to go onto the biggest chainring, or it won't go onto the smallest.

Since I've never been all that crazy about the Simplex anyway, I'm thinking about upgrading. What puzzles me is the dropouts. They aren't branded "Simplex"; the only engraving on the dropouts I can see looks like "CO". What's also weird is, the rear derailleur isn't just screwed directly into the dropout, there's some sort of washer with a built-in stop between the derailleur and the dropout. My experience with this stuff is pretty limited; usually in the past I've worked on maintaining the parts I had, rather than replacing them. My wife's Grand Touring has Suntour dropouts and Suntour derailleurs, and I had expected my bike's dropouts to be branded "simplex" but it looks to me like something else is going on.

Anybody know what I've got here? I'd love to switch to Huret something, since my last two vintage roadbikes had Huret derailleurs and I like their action a lot more. And it would be at least keeping my GJ as French as possible. What else might be compatible without too much fiddling?