Early (pre-1900) Monkey Wrenches

[Dave Cannon]

Looking for help identifying an early monkey wrench. It has no name or trademark — although there are a couple of symbols on one side. Pouring over online image search engines has not yielded any clues. The wrench is 7" in length.

I gave my son and old wrench last year that turned out to be a railroad wrench from the 1890's, but this one has me stumped so far.