Hello SonofOrange,I have a copy of the original bill of sale on my L245F, it gives the month and year it was imported - April, 1977. I have it because my Dad tracked it down through the selling dealer that happened to still be around. He was able to do that because Kubota corp keeps records of all units sold. So the key is to get friendly with someone inside Kubota Service.
It's interesting to know, but what matters more is the life the equipment had since then. Mine was sold new to a concrete plant in Florida. Where it worked for 32 years. It had sand everywhere it should never have sand.
I would guess that the most common need to determine a tractors age (other than your own curiosity ) is to confirm what you are being told by someone selling a used machine. I have found that it you ask Kubota politely, they will provide the information quickly.
It is interesting to me that now that they are using a 17 digit "vin", they are keeping the "code" dealer only.