There were a couple versions. Mine is a single arm on a Record
derailleur(1963) with one Cyclo and one Benelux pulley .Later ones were
double sided and used the Campy pulleys.
First Rally derailleur I saw was 1973/74 at Fulton st cyclery in SF and I recall it came from the Taylor bros in theUK
gray overcast in PETALUMA,CA USA
former Egg capital of Norcal and home to many Jewish egg farmers in the day