Does it have 4 or 6 inch belts? If it has 6 inch belts, it is a 1500A which is what we have. However, both models are very similar. Gehl also made some of these baler for Ford. Dad bought ours new in 1977 and we still roll all our hay with it. I won't say I like it, but it gets the job done. The bales look pretty good right out of the baler, but they'll flatten out a little bit after sitting a few days.
It takes some experience to do a good job with these balers. You have to keep the roll pretty square or it'll get cock eyed and you'll have to dump it and start over. I've heard people complain that it's hard to start bales, but I've never had that problem. I suspect that theirs was out of adjustment. These balers were closed throat, which means the hay must be good and dry or it will wrap around the rollers and you'll spend an hour or two cutting it back off!
I've used this baler so much I guess I could talk all day about it, so if you want more advice email me and you can even call me if you'd like. I've looked at newer baler several times, which do a better job and are easier to operate, but then I look at the price tag and keep ours another year. I think ours was $3500 brand new and now they're $20,000 or more.
If you're looking for a cheap big round baler, you'd probably be alright with the Gehl, a JD 510, or a Vermeer. I never did like the old New Hollands. They just wouldn't roll a very tight bale until they added the air bags on the newer models. Any of the old models are going to be aggravating, so I wouldn't pay more than $1000. A late 80's model baler (JD, Gehl, Vermeer) usually run $5000 to $8000, but are a lot better.
I hope I've helped and not confused you. Good luck.