If you're referring to that end that
kinda sorta resembles a short-jawed open end wrench, it looks to me like a PO might've chopped off the handle of a standard adjustable "S" wrench, a 12 incher, probably a Westcott, just where the opposite curve started. On some models that part of the handle was solid, like the first curve, on others it was hollow, probably to decrease the weight of the wrench, or possibly just for aesthetics. Maybe it was twisted, or maybe it was fine and the PO who made the mod just had a wild hair idea.
EDIT: I don't have any adjustable "S" wrenches with hollow handles, but for a visual of what I am describing and what that wrench looked like originally, if you're having a hard time following what I am saying, there are several on HeelSpur's board, here...
https://www.garagejournal.com/forum/threads/6-curved-adjustable-wrenches.501949/