Series 504 model 250. There should be a tag on it saying something like I4-80. That would identify the exact configuration. Just from the picture, I would say it is a Later I4-80. PTO driven twine tie and the auger is belt driven. May have rollers on the plunger. Early models were wood guides.
From the looks of the prairie, your way to far from me, I had one just like it and it was a great little baler. Many / most needed parts can be crossed to a NH and easy to work on. Worth way more than you will get for it IMHO.