This is a Simplex Tour de France from the period 1948 to 1956. I could not read the lettering on the arm - if LE it is probably pre 1951 if JUY it will be '51 or later. The Simplex rear mechs are not difficult generally to identify and if any body needs help with these I also have original instruction sheets for most models which I can photocopy. The Champion du Monde name was only used for a couple of years after WWII - first for the single pulley model which was practically identical to the prewar Champion du Monde and then for the Champion du Monde 46 which ran from 1946 to 1948 and was the first twin pulley racing Simplex rear derailleur. I have a NOS one up on Ebay for sale at present with a Simplex front derailleur of the same period:
> Scott typed:
>> Just got this from a mate in England. Would love to know its age
>> and model name.
>> many thanks
> Roy Drinkwater replied:
Looks like a Tour de France model of 1946-54. "The Dancing
> Chain" states:
> Simplex changed derailleur names frequently. Identifying and
> dating Simplex derailleurs vexes today's historians and collectors.
> Simplex sometimes tacked a number onto the name to denote the year of
> first manufacture. Dozens of slightly different rear derailleurs
> were called Champion de Monde (World Champion) or Tour de France."