Other than a few numbers and W Germany, no markings
Works via a spring loaded wedge. You slide the moving jaw with your finger and it stays where it stops. To loosen you push on the point of the wedge - sometimes you have to tap it with something.
I'm leaning towards Dorn or Instant-Grip. I've seen similar on the interwebz but can't find a match for this.
FWIW, great little tool (8") unlike a regular adjustable wrench this has absolutely no play in the jaws at all.