It does have some Rushton-y features, like the wider stem, and wide sheer plank. I can't tell, but if the planking is also flush with the tips of the ribs, that would also be a clue. Rail caps would also be consistent with b grade.
What isn't Rushton-y is the square stern seat. Should be trapezoid (is it a replacement?). Bow seat should be mounted on a cleat. At least one stem stem should have the maker's mark and a serial number.
Note that the similar deck shown on my site is mounted in a lapstrake Nessmuk model, so it is not necessarily a direct comparison.
Oral histories are always suspect. 1918 would put the build date right after Rushton closed and before St. Lawrence started up again. However, a number were built be emnployees - I tried to by a Clarence Brown (marked) at Assembly a few years ago, but the owner thought it was made of platinum.
I don't think it is Canadian. Tapered gunwales aren't really known north of the border.
Dan