Victor,
Early Campy #626 clamp-on double cable guides featured a small tube on the right (for bare rear deraillleur cable) and a cable housing stop on the left - to run a short stretch of housed cable to the Record front derailleur's cable housing stop... I assume you were referring to the derailleur with the long "Tail" hanging down.
Those guides date back to the late 1950s - or perhaps even earlier - and are a bit difficult to find these days (of course, so are the early derailleurs).
I believe that by the late 1960s those guides were completely dropped by Campy and replaced by #626/A which just had open guides on both sides.
I think that the black plastic Simplex Prestige double guides were the last to feature a cable housing stop on the non-drive side - for their nasty old push-rod style Prestige front derailleurs... which they still produced well into the 1970s (about 10 years too long).
There seem to be plenty of those guides available - NOS (and cheap)... if you just wanted to run a cable correctly while seeking that #626 Holy Grail.
Good Luck!
Bob Hanson, Albuquerque, New Mexico, USA