Ditto, repurposed wrench. If you read the old literature, there are lots of articles on how to salvage your worn out wrench by grinding it to a bigger size.
>I believe it had to be done in a shop with a milling machine
Don't underestimate what can be done with a slow grinding wheel, a jig, and lots of patience. For that matter, I've seen amazing blacksmith work done primarily with a file, stuff you would swear came off some machine..
There were a lot of poor farmers and mechanics with more time than money...