Leon Fisk writes:

The vise below is foot operated, built similar to leg vises. The second
slide is a video. When watching I thought the front jaw insert was
loose but now I think it is deliberate to allow the jaw to stay aligned
with its mate. One could probably do something similar for the leg
vises...

https://www.instagram.com/p/Bb7H9o7jzRq/

My browser doesn't render instagram but from your text: Does the vise
also have a ca. 4"x4" shelf-like projection? Could be a farrier's
caulking vise. They have that self-aligning jaw and treadle closure.
I had one 50 years ago but swapped it off for some other stuff.

The shelf would have held a "caulking block", a steel brick with
acute-angle grooves, used to support a freshly caulked shoe, caulk
down, when hammering on the hoof side.

I've also seen a foot operated vise in an optical repair shop but it
was an elegant precision tool, far from clunky old iron.

--
Mike Spencer Nova Scotia, Canada