Giant vise

[Toolmaker51]

Now that's a vise! The serrated jaws and nut on the moving side tell me it is cam operated jaw. The screw gets size close, the operator locks material with a simple motion. With the flat sides it can be mounted vertically too; that is not very common.
In shot with caliper for scale, about an 8" 200mm opening, an roughly as wide. And jaws are removable, for soft jaws, fixtures and other convenient workholding.