This is a pair of adjustable pliers based on a rotating tongue-and-grove mechanism. They are fully functional, and are especially useful in cases when non-marring tools are required.
The form of these pliers, especially in terms of the handle shape and ergonomics, is derived from a very old pair of pliers manufactured by the Diamond Tool and Horseshoe company. However, the adjustment mechanism is of a more modern style, and is identical in principle to modern commercial products available from many manufacturers.
This model may be scaled as needed depending on your needs, and functions well at any size.