Weight codes used 1929-1979
1929-1930 - most were simply numeric, however 'A' through 'D' used; exact weights not known; heaviest vehicles received 'A', lightest 'D'; weight code was a suffix (after the numbers)
1931 - 'A', 'B', 'F', 'L' are known as a prefix, but exact classification not known; argument over if it was indeed a weight code; expected to be similar to '29-'30.
1932-1935 - 'A' through 'E' are know as suffix, but exact classification not known; expected to be similar to '29-'30.
1936-1937 - exact weight codes not known
The 1971-base (and later years) received validation stickers. The weight class code was the first letter of the serial number of the plate from 1971-1979. The validation sticker also had the weight class letter. Weight classes were discontinued in 1979. Unknown if 1980-1982 original issues continued the plate-number weight class.