Finding the model number on old cub cadet 128

[Carpetbagger]

I've found the serial number for my cub and the serial number for the Kohler 12 hp motor. Where can I find the model number for the tractor?

 

[Shaneard]

128 Serial Numbers
Location: Tractor's rear-drive housing, or the left side of the tractor frame (after February 1974).
1971: 400001
1972: 417643
1973: 457305
1974: 495749
Final: 529811