Seems like you're on the money, JC.
Thanks to Jerry, I got a copy of the Classic Dirt Bike article on them that claims that the first TF1 was a 1980 model and was also the first one in orange.
Seems to add up as the original forks that came with it are orange as are the original footpegs.
Without any numbers though, it's hard to prove exactly what it is but I'd reckon 1980 TF1 would be pretty close.
At least I know it doesn't fit into pre 80 if I choose to ride VMX on it at all.
Thanks again for all the input, gentlemen.