NH made the 76 which had canvas curtins to take the hay up instead of spring fingers on chains, which the later 77 used. There were 77s and Super 77s. I had a Super. It had the plunger riding on rollers instead of wooden slides and also made large, well shaped bales from any sized windrow. The 77s dated from the early 1950s. Don't know about the 76s.
The NH 66 and Super 66 were sold about the same time as the 77s. I'm reasonably sure they were the first side fed NH balers. These balers use an auger cross feed.
I think the IHC 45 baler dates from about the same time. It also used an auger cross feed, but the one a neighbor had(powered by a Cub engine) did not tie well. The NH balers tied well from the beginning.
Case had a pickup baler with the spring pickup teeth in the early 1950s which fed the hay into the chamber from the side, maybe with an auger. Early ones did not have automatic tieing, but had a seat on each side of the bale case where two men wire tied each bale like on the older hand fed balers. Very soon Case put on knotters on that basic baler. Must have been a dusty job wire tieing. My guess is that the hand operated baler dated from the 1940s.
John Deere in the early 1950s had a baler that fed directly into the bale chamber and had the bale cas extending to one side. They had both twine and wire tie. Don't know the model numbers.
I think the work on the NH 76 balers started before World War II, but I may be wrong.