If I may chime in, I think what has happened is your tractor at one point in its life has had the "bathtub" frame swapped out because it was damaged or broke. My MH 55 is kind of like your 44, when I bought it it had a diesel serial number on the frame, but the tractor was a gas burner. After cleaning all the grease and other junk off of the transmission housing I found the true serial number for tractor. As Gary and John B said, there should be a serial number stamped near the clutch pedal. If those numbers do not match what's on the tag on the frame, then I think its safe to say it was a case of someone changing some parts.