Penn Yan used the first two digits to designate the year of manufacture immediately after WWII. I have seen the date used as early as 1946. The boat or canoe would almost always have a space after the numbers indicating the date and the numbers following. After circa 1957, PY no longer indicated the date of manufacture, but simply had numbers. Nobody, so far as I know, has figured out any scheme. My guess is that your canoe was made some time after 1957.