French Patent # 2,520,693 - Simplex

French Patent 2,520,693 - Simplex main image

As far as I understand it this patent covers a number of design features of plastic pulley cage plates.

Simplex did not produce plastic pulley cage plates exactly as depicted here - but it did fit slightly different plastic pulley cage plates on its lower end derailleurs from about 1983. You can see them on the Simplex SX1 T/P depicted here.