[Dixie Gunsmithing]

I may be wrong, but the stamps looks to be naval ordnance. It looks like its made to either clamp the outside or inside of a part on a slide way, and maybe on a pistol. I've never seen that design, but that don't mean they didn't make it in-house, and never cataloged it.

Added: This design could be used to make an adjustable lap for a slide or a frame. Place some compound in the ways, slightly tighten the tool down in it, and run it forward and back to achieve a lapped surface.