Indeed, the "Dural Forge"-lettered brakes were RACERS. In the old days, Mafac didn't bother to put the name on the brake - they made two models: cantilevers (in two lengths) and centerpulls, which were forged and thus labeled so. By the late-60s or early 70s, they realized that with all their newer models, this could lead to confusion, so they labeled them just like the others. The switch to plastic bushings seems to precede the re-lettering slightly. (I have a set of "Dural Forge" with plastic bushings.)
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Jan Heine, Seattle
Editor/Publisher
Vintage Bicycle Quarterly
http://www.mindspring.com/
My 1966 PX-10E has "dural forge" brakes with bronze bushings. I also own two complete NIB sets of Racers. Except for the lettering they are externally indistinguishable from the brakes on the bike.
jeverett3@earthlink.net (John V. Everett)