Lennard,
I believe that the wrench that you show, is a much later made wrench.
compare yours with the pictures of the ones from Davistown Museum in Liberty Maine
and the ones in the pictures supplied by Herb Page.
I am refering to the construction of the movable jaw, look closely at the ring around the
handle and the brace. your brace is the only one with a round rod and it is pinned together,
whereas the othors look like an open loop.
the threads should give you some indication to the era of manufacture also.
p.s. I have been to the Davistown Museum, it's a small but interesting place, lots of old
made in Maine tools.
it is right accross the street from Liberty Tool store. home of old/user tools for sale.