I've just spent a couple of hours happily cleaning and gently polishing a Huret Jubilee rear derailleur. I'm amazed by the thing, to be honest. Despite being on a bike that has been neglected pretty badly, it shined up VERY nicely.
I also have a question - is there a trick to removing the upper, toothed pulley from the inner cage plate? Is it threaded in, or is mine just sort of rusted into place?