I came across this Armstrong wrench in a box of car parts. I see a few posts about Armstrong wrenches, but don't know anything about the company.
I don't know much. I have a 12 inch adjustable by Armstrong. It is the heaviest 12 inch I own.
http://alloy-artifacts.org/armstrong-bros.html#history (http://alloy-artifacts.org/armstrong-bros.html#history)
The square shape indicates it was for a square nut or cap screw, quite possibly the set screw on a machine or the like.