I bought this at a yard sale and I thought it was a lineman's wrench. I tried it on some assorted line hardware in my back yard and it doesn't seem to fit many of the standard bolts/nuts.
It fits square nuts 1/2", 3/4", and 1". The hex holes seem to measure for 3/4", 1", 1-1/16", and 1-3/16". It is marked "KEN TOOL C-30". I'm not totally sure about the C in C-30 as the embossing is not very clear.
I looked in a 1950s line supply catalog. but don't see anything like it in there. Can anyone help me out on this?