Jan Heine said "...The late 1940s Mayeux also has a (cable-operated) front derailleur with a triple crankset. I am not sure who made that one, but it looks like a factory-made item with a big return spring. Perhaps Spirax? I'd have to look through my old magazines..."
Another candidate for a triple-capable vintage front derailleur....
The 1930s Cyclo catalogues show Rosa triple chainwheels and a Rosa cable-operated front derailleur stated to work for triples.
The 1950s Cyclo catalogues don't show or speak of triples as I mentioned in previous email.
Peter Brueggeman
La Jolla California USA
4peebee(at)peterbrueggeman.com