rare unusual antique C clamp w/ quick adjustment release jaws, vintage woodworkers tool

Vintage C clamp, 14" long overall, 8" jaw, 4" throat. This has no makers marks or patent numbers / dates that I could see. I've been told that this is a very unusual design for a C clamp, with a quick adjustment / release with the jaws on the screw.

This looks early 20th century vintage to me, from the weight and general patina to the casting. There's a makers flaw (see photos), this may have been a prototype or sample piece. It's been used in a workshop, has a few spots of old paint to the finish.