>Here's another view of Jean Robic on his way to victory in the 1950
>World Cyclocross Championships.
>
>This particular bike appears to have MAFAC centerpull brakes up front,
and cantilevers in back.
The centerpulls look very different from any Mafac production model. According to Le Cycliste, the first Mafac "Racer" centerpulls were brand-new in late 1951, so they were not out yet in 1950. Perhaps a prototype? There were other centerpulls before Mafac, too, I believe. (Side note: The first Mafac "Racer" brakes were not marked "Racer," but the ads called them by that name.)
Also note how the bike has wingnuts on the front, but does not appear to have any on the rear. The peculiar shape of the wingnuts remind me of some I once saw on a Derche, which were marked with two letters, the last being "D." Sorry my memory is cloudy there. I never have seen these wingnuts on any other bike and wonder whether the letters are the initials of the constructeur Derche. The bike had many proprietary parts.
I don't think that is evidence enough to suggest that Vietto's bike or even his front wheel was made by Derche.
Anybody got an idea regarding the derailleur and shifting system. It appears to use a downtube shifter - definitely no bar-ends and associated cables on his bike. -- Jan Heine Editor Bicycle Quarterly 140 Lakeside Ave #C Seattle WA 98122 http://www.bikequarterly.com