The serial number on a Gibson Model D tractor is located on the metal frame rail on the right-hand side of the tractor. The first stamped letter is the model number, and the following numbers signify the production year of the tractor.
Wilbur Gibson founded the Gibson Manufacturing Corporation in 1946 in Longmont, Colorado. This company produced the Model D tractors as its second model after the Model A. The company produced the Model D from 1947 to 1949.
Gibson manufactured its Model D tractors with a 46-inch wheel base, and each one weighed 955 pounds. They were steered with a lever, and many owners chose to purchase an optional steering wheel attachment.