I tried to find information on this but didn't find any thing
IT IS 15" Long  fits a 3" nut

 Size and Kenosha says milking machine. Tri-clover has a 25H2 wrench if my memory serves me correctly.

The dairy equipment (pipelines, bulk tanks, etc. ) wrenches tended to be aluminum or other light weight alloy rather than malleable iron.

This one is malleable iron weighs 3 lbs 5.4 oz

Haven't been able to identify definitively but Specialty Brass Co of Kenosha,Wi made the Nofome Milk Pump and other dairy fittings. Assuming S B Co may be Specialty Brass Co. I agree with Stan that most milking machine wrenchs were aluminum and don't know that Specialty Brass Co cast malleable but they did have foundry in Kenosha.

My  memory is not photographic Tri Clover wrenchs are 25h3 and 25HA2 They are aluminum based.
The Cherry Burrell and New Rockford are malleable. Cherry Burrell made dairy related items but don't know if New Rockford did or not.

 Missed this one in looking for dairy wrenchs. It is Tri-Clover 25H 1 1/2 and it is malleable casting.