I think the real issue for this series of tractor is when they quit calling it a Thirty and started calling it an R4. I have a wide-gauge Thirty from the same 6G series. It's raining outside, so I'm not going out to check, but I believe the serial number is 6G763W, so the changeover must have been somewhere between your tractor and mine. I hope mine will look as good as yours someday!