Only the newer machines are rotary type and they usually include a "R" in the model number I believe they now sell a R75-newest biggest and the R65 newest next smaller for lastest series. Before that series came the R72-biggest, R62-next smaller, R52-next smaller, and then R42-smallest for that series. Before that came the R60, R50, and R40 for that series. And finally the first rotary series were N7, N6, and N5. These were the only rotaries named with out the R in model number and were built from 1978-1984. I think most of this is correct info, but some else on this site may be able to do the rotary combines better justice than I can. The newer conventional machines contained a "C" in the model number (C72, C62, and C52IJIJ) The older conventional models are numerous and use an aphabetic character which is sometimes followed by a series number. l3-biggest, M3-next smaller, and F3smallest for 3series were built from 1983-1986. The l2, M2, F2, and K2 were built from 1977-1982, except the K2 which ended in 1981. The l was built from 1972-1976, the M was built from 1973-1976, the F was built from 1968-1976, and the K was built from 1969-1976, the EIII was only built in 1968, The G was built from 1968-1972, The E was built from 1962-1967, the AII and CII were built from 1964-1967, the C was built from 1960-1963, the A was built from 1951-1963, the R was built from 1951-1960, the B was built from 1953-1963. Size of the conventional models is as follows: A,AII, B, E, E, EIII, K, and K2 models were all 3 straw walker wide designs. The R used a raddle chain instead of walkers. The E and EIII were 4 cylinder 226 cu gas engine, rest had 6 cylinger gas engines, except an optional 4 cylinder 200 cu diesel offered in the K2. 8-15' headers and 2-3row cornheads. C,CII, F,F2,F3,M,M2,and M3 models were all 4 straw walker wide designs. The M models had open bottom walkers for greater capacity. The F2 and F3 used a 4 cylinder diesel 200 cu engine, the rest used 6 cylinder gas or diesel, except the M which was also offered with a v8 350 cu gas engine. 12-24' headers and 2-6row cornheads G,l,l2,and l3 models were all 5 straw walker designs and I think the G was the only one with closed straw walker bottoms. The G and l offered the use of the v8 350 cu gas engine, the rest offered 6 cylinder diesel engines. 13-24' headers and 4-8row cornheads.