I've been unable to find a Simplex database to answer this question. I've acquired a Simplex Juy derailleur that appears to have no number. It has only one pulley, a telescoping spring in a banded coil, a tension spring, a hanger and a chain that attaches to a cable.It reads Simplex, Juy Made in France. Conditon is good. Unfortunately I haven't followed the "Juy" discussions close enough to know what it is I have.(the Holy Grail?) I have pics if someone wants to see it.
TIA
Warren Young