I feel like this is a farm equipment wrench but mark is not plain. It has "85" on side with mark that looks like two letters inside a G or Q. It measures 6" long with 1" and 1 1/4" open ends and a 3/8" square opening.
Possibly a wrench for oxygen/acetylene tanks?
Seems like a bottle wrench...yes....Presume the G is for Something Something Gas