If you post your serial number I can probably help you out. I have a fair amount of original dealership paperwork and books on the Versy swathers up to and including the 4400 series, been a long time since I looked at it, but as I recall, there is a page in the front of the parts binder with the breakdown of numbers. If you do post the number, I will dig things out when I have a chance so may be a day or more. I would say it must be early version that the year is not stamped on the serial number tag. Not sure when they started doing this, but I think it was mid 70s.
Contracts are made to be broken, a handshake is the law of God.