Tom,
Don't know what it is about old dictiphone foot switches, but I use one as
well. It has a plate on it that says "Edison Company, East Orange, New
Jersey" so that's pretty neat.
I never cared for vox, and use the foot switch 100% of the time for ssb.
Yes, that extra jack on the Heil mic will take a 1/4 mono plug to connect a
foot or hand switch. If the switch you get is too small, glue or screw
it to a piece of plywood to keep it in place or you will spend too much
time playing footsie with it as you feel around under the desk trying to
find it
73 Steve KW3A