i only spent one summer with one of these but they were such a help. the summer of '76 we had to cut hay elsewhere and haul it because of the drought and we worked with a couple of neighbors who had square balers and these stookers and we cut and loaded about 2500 acres of hay onto flatbed semis for hauling 200+ miles.
What this machine does is stack the bales at an angle automatically as they get pushed out of the baler. It stacks three on the bottom, then 2 and then one on top making a nice triangle. The key to how they work is that only a corner of the bale is sitting on the ground allowing air to get at all sides so you can bale a little tough and it will dry. they also shed some rain which a bale lying on the ground does not. They also are so easy to pick up with a loader and put on a trailer or truck or whatever - six at a time.
Yours looks to be in pretty good condition. Although I cannot see the details in the photo all the main parts appear to be there. For me the neat thing was the simplicity - fully automatic with no moving parts. There is a market for these thing sin various parts of the country, the problem is that many people do not even know they exist or what they will do for them. If you are going to handle square bales without a full blown stacker, this is the way to do it. You do not have those very dangerous haywagons, you can do the job with a lot less people, and if it takes you a few days to get your bales inside you will not lose them.