Originally Posted by
T-Mar
The serial number indicates October 1979 frame manufacture. That's late enough in the calendar year that it should be a 1980 model. By this time, Simplex had introduced a version of their droput with a integral derailleur stop and factory threading, to accommodate non-Simplex derailleurs. This may be what you have, though I wouldn't expect one on a Peugeot.
My 1980 PKN-10 happily took a SunTour Cyclone II rear derailleur, no problem.
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"Far and away the best prize that life offers is the chance to work hard at work worth doing." --Theodore Roosevelt
Capo: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger (2), S/N 42624, 42597
Carlton: 1962 Franco Suisse, S/N K7911
Peugeot: 1970 UO-8, S/N 0010468
Bianchi: 1982 Campione d'Italia, S/N 1.M9914
Schwinn: 1988 Project KOM-10, S/N F804069