I found this 8-inch monkey wrench recently. The only characteristic that I find remarkable is that the frame is made out of formed steel with a dovetail joint at the front. In every previous monkey wrench I've found, the frame is usually a one-piece forging or casting.
There's very little information on the manufacturer. The Tool Archives traces it back to at least 1918, and reports that the Larco trademark was registered in 1920. I don't know why it includes a large "W."
Fortunately, Mister G had published a previous post featuring a 1921 advertisement in which they boast "Greatest improvement in wrench construction in 50 years." Sorry, but it doesn't seem that special to me. The only other ad I could find was from 1926, indicating that the company made a range of plumbing supplies:
|The Frisco Employes' [sic] Magazine, July 1926|