Hello Snoopy, while it could be a different wrench, the tiny square hole screams acetylene, it could also be a for valve stem. IMO the small square is key to ID.While it could possibly be an Acetylene wrench, I'm more inclined to think that it is an implement wrench. Do a google search for "vintage implement wrench" and you'll find a huge array of specially designed tools that used to be included with specialty implements and other farm equipment. Literally thousands of different designs.........
https://www.google.ca/search?q=vint...VygG_kYHICw&ved=0CAkQ_AUoAQ&biw=2560&bih=1475
Here's one site that specializes in antique farm wrenches and you'll see how varied the wrench designs are. It may be hard to find a specific purpose for this wrench unless there are some markings on it.
Antique Farm and Patented Wrenches and Other Collectible Tools for Sale