Simplex did try to get into indexed shifting, surprisingly quite early in the 80's with this:
VeloBase.com - Component: Simplex Selematic 5
But I suspect, like many early attempts by other makers, it did not work that well, plus, the humungous proportions of the RD must have not impressed that many people.....
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72 Line Seeker
83 Davidson Signature
84 Peugeot PSV
84 Peugeot PY10FC
84 Gitane Tour de France.
85 Vitus Plus Carbone 7
86 ALAN Record Carbonio
86 Medici Aerodynamic (Project)
88 Pinarello Montello
89 Bottecchia Professional Chorus SL
95 Trek 5500 OCLV (Project)