When they came out with the first R40's and 50's, they were a whole new combine. Prior to that, there was the N5 and R5, but no Class 4 rotary. I tend to think they put the small P3 out here for all of us to try, keeping the P1 in the big boys, until they found out it actually worked well without the cage sweep, etc. Then they decided to use the P3 concept in the 60's and 70's. The Hawk Series marked the introduction of the P3 in the big combines. Also went to a white_grey cab interior instead of the tan. I don't remember what, if any, other changes there were. Tom langan