Mafac Racers at first weren't marked as such, because there were no other Mafac centerpulls. The earliest examples, with a more square arm shape (some very early ones with oiler holes for the pivots) are rather rare. The later ones, basically the same as the later Racers marked "Racer" aren't so rare. They are the same brake, only some time around the appearance of the stamped name, bronze bushings were replaced by plastic.
Jan Heine, Seattle