Measure the extreme overall length, width at the widest point and depth in the center. A side view photo that shows the stem profile would be helpful also. Look on the stem inside the canoe, at both ends, directly below the decks (first photo in post #3 above) to see if there are any numbers or a name stamped there. It may be difficult to read. Where is the canoe located? Most canoes never traveled far from where they were first sold and the location can be a clue to the manufacturer.
Thanks for posting. These mystery canoes are always interesting.