Are you sure you don't have the dimensions on the right side reversed?  From here, the right side looks like it's splayed out; of course, that may be because I'm standing so far away*.  And, if they are reversed, I'd say the wrench probably started out life in better shape and got stressed and bent.

*Now I'll find out you live on the next street over from me; ah, the internet.

ahhh...I did...and fourth is spelt forth...I gimp fail, lol.

Frank Mossberg among many other tool makers sold stamped steel wrenches as both hardware store open stocks and to machine makers as OEM tool kits.     Marked for maker, buyer or simply unmarked to save a few cents maybe.

     Dodge even started using stamped steel wrenches after 1928 to save a bit on tool kit costs.
I tend to believe unmarked are either specific machine or budget hardware store open stocks.
   Dating such an item could be 1900 to 1950 without any markings to go on.     The local AutoZone still has new stamped steel wrenches for fan clutch use.    So anything is possible really.

    Form is the only clue you have left, start with F. Mossberg and the other old companies better known for stamped steel products.     Somebody has to be a dead ringer.