Miscut. Even though notes of the 1937 series were printed in sheets and cut using machinery, machines don't always make perfect rectangles. Oddly enough, the later multicolour series exhibits many notes with crooked borders, and sometimes the edges don't make 90 degree angles. Replacement notes often have the worst cuts, like the note shown below. The top and bottom edges are aligned to the horizontal but the left and right edges are not quite vertical, so none of the corners are 90 degrees, and the shape of the note is more like a parallelogram than a rectangle. That is in addition to the design on the note being rotated out of alignment, leaving slanted edges all around.
Consequently, notes vary in size and it is not entirely correct to say that if a note does not reach a certain set of dimensions, therefore it is trimmed. I always stress the rule of thumb that states if a note looks trimmed, then it is trimmed. The 1937 $1 note at the top of this thread has wide edges, so it doesn't look trimmed. In fact, it could use a trim of the top edge to get it straight and therefore more aesthetically pleasing. Washing tends to stretch notes, not shrink them because banknote paper is pre-shrunk. A dealer once showed me a 1967 $1 note that was freakishly stretched. It had to be about 10% longer than an average note. Wetting the paper makes it swell, then pressing it keeps it spread out while it dries. I'm sure the note I was shown by the dealer had to have been treated with additional tension since banknote paper has a much higher tensile strength than, say, newsprint. So if you think a note has to be at least a certain size to be original, you could be sadly mistaken.
{http://www.give-a-buck.com/ebid/bank_of_canada/5/bc-48bA-cs0369.jpg}
