interesting C clamp, on one side of the main casting it says GRAND DualGrip
REG US PAT OFF, on the other side it says 40A and 40 (presumably casting
numbers), and QUIKCET Pat Pend.  max opening is 4 inches. The copper colored
parts were probably nickle plated, I polished them and there is a little
silver still visible.

to operate, squeeze, slide the clamp bar down, release (spring force pushes
it together) and tighten the screw.  to release, loosen screw and rotate
clamp bar 90 deg to disengage ratchet.