These tractors were produced for 21 years--1958 (year I was born) through 1979 (year I was married)--and the serial number, found on a plate on the left side of the bell housing, identifies the year of manufacture (see pasted chart). I can only lift my 16-disc harrow a few inches off the ground. Remember that although these are tough little tractors, they're only about 20 hp and 2wd. That's not very much power in lifting an implement weighing 500-600 pounds. Instead of lifting the disc and carrying it to the tillage site, I just let it touch the ground and let the discs take part of the weight.
1958: 501
1959: 2011
1960: 8082
1961: 11168
1962: 16637
1963: 21181
1964: 25387
1965: 28408
1966: 31285
1967: 34818
1968: 37352
1969: 39906
1970: 42300
1971: 44424
1972: 46605
1973: 48507
1974: 50720
1975: 54273
1976: 57773
1977: 60839
1978: 63111
1979: 64544