The Schwinn GT400 Le Tour was manufactured for Schwinn by Shimano. In the Shimano hierarchy this derailleur was called the Shimano 500. It shared the geometry (and much else) of the Shimano Crane and Shimano Titlist, but had steel pulley cage plates (unlike the Crane) and steel parallelogram plates (unlike both the Crane and the Titlist). As part of Schwinn’s requirements the GT400 Le Tour has an adjustable cable outer stop (something Schwinn re-taught Shimano - and which Shimano also adopted on the Shimano 500).
Schwinn sold this derailleur as an upgrade product - and it was widely welcomed by Schwinn users who had had to put up with the Schwinn Sprint and Schwinn GT200 (both were the dreaded Huret Allvit travelling under an alias).
This example has a very mysterious two letter date code of ‘YI’ which should indicate 1979, but makes no sense to me.
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