Rotobaler Questions

After many years i was finally able to find a rotobaler at an auction not far from me, close enough i was able to pull it home! I had to give a whole $40 to outbid the scrap guy but I was fine with that besides he got plenty of other stuff. It’s been sitting outside for many years, someone started at one point to repair and restore things. I spoke with the older gentleman I bought it from and he never used it, had intentions to restore it but like most of us he had too many other projects. I think most of the pieces are there he even had a couple of the ball hitches. Apron chain has a broken cross piece which i should be able to weld. My plans are to hopefully get this thing back up and running and make 20-25 straw bales a year with it. I have read plenty of the postings on this forum as to where to start with repairs and freeing things up, which i started on already. I can turn the lower press roller with a wrench on the end so i think things are freed up. Now for the first batch of what I'm going to guess will be many-many questions posted here. Does anyone know the size of the v-belt that goes on the side from the apron to the twine arm? This is missing while I'm sure I could figure it out but if someone knows it would help. Is there any other way to date these other than the serial number? The bracket on the back that has the number is painted over, the manual I got when I bought it say #2986 which would make it a 1947 but who knows if that's the right number.