I have this particular wrench, Patent No. 1798194. 1,1/2 in. No. 3 B.B. Wrench. You are right. It was used to build Bridges over the Welland Canal. We found it while diving in the canal, under one of the Bridges in Welland Ontario.
demps@cogeco.ca
rdempsey@seaway.ca
PS. I work at the canal. 36 Years and counting.