SIMPLEX SUPER LJ SLJ PX PY 10 rear derailleur Mercier Gitane

The SLJ PX PY designation on a SUPER LJ body

The SIMPLEX SUPER LJ rear derailleur appears here with the SLJ PX PY marking, a reference found on components fitted to Mercier and Gitane bicycles. This is a used part, and the photos are an integral part of the description: they document the surface condition, the cage, and the pivot areas precisely as they are.

For a restoration, this unit answers the need for a period-correct SUPER LJ rather than a later substitute. The existing marks and wear are part of its history. The images show the current state, so you can assess the cage and pulley wheels without guesswork.

Why this rear derailleur matters for a build

Restorers look for the SUPER LJ family because it places a bicycle in a defined period. The SLJ PX PY detail narrows the match to specific drivetrain configurations. Rather than a generic replacement, this is a component with a legible identity.

Condition is central. Every photo contributes to the record: pivot, spring housing, cage profile, and the manufacturer's stamping are all visible. No hidden claim replaces what the images show.

If your project pairs it with a complete drivetrain, look also at the Derailleurs category. A related option is the Simplex rear derailleur vintage bicycle Eroica Peugeot Gitane Mercier, and for the cockpit side, the SIMPLEX vintage gear shifters 1970 PX/PY 10 EROICA can complete the setup.