Offlist, Don Gillies asked (and I hope it appropriate to credit him for the question):
"Is the campy front mech the 1st parallelogram front mech ??"
This time, I actually did some "research," revisiting the Dancing Chain and the wonderful pictures from Arnfried Schmitz at
http://www.users.globalnet.co.uk/
The most surprising thing about Dancing Chain and Schmitz is how shabbily the fronts are treated, as orphans only rarely worth a picture.
I found no early parallelogram fronts in Herr Schmitz's collection, and the earliest I found grazing forward in time from the 30s in Dancing Chain was the Huret, cited as 1960. I believe I remember working on Hurets in 1962, it was the next year before I saw pictures of the New Campy Record. Ironically, the Dancing Chain's picture is of a later, slicker, model with two adjusting screws. The first one (of which I still have an appropriately "weathered" example) had a single (inside) adjusting screw. The outer throw was adjusted by sliding the cage, much as on a Campy plunger type.
Before about 1960, everything I've seen pictured or in person was plunger type, including both arm activated (which we called "slap shifters") or cable operated with a helical plunger like so many Simplex and Cyclo rears.
your mileage may vary.
harvey sachs
mcLean va