I have a similar, but smaller, key wrench, e.g. it also uses a tapered key to hold an adjustment position. Mine is an earlier hand-forged tool made of iron. The design principle of using a key to lock adjusted jaw openings was originated as early as the late 18th century, and remained in use into the twentieth century. In 1903, Loring Coes, obtained a patent covering his well-known Coes Key Model. This model, which used a screw to adjust its jaws and a key to lock the adjusted jaws, came originally in 28, 36, and 48 inch lengths .
