The tractor in question is an International TD18 - a model which was replaced by the TD18A in 1950/51. The model had its first Nebraska test in March, 1939. The tractor is easily recognised by the mounting pads on the track frame, the five track rollers and the twin exhaust pipes denoting the 6 cylinder engine - it is very similar to an International TD14, however, those only had a 4 cylinder engine with one exhaust pipe. 

The photo of the tractor pulling a logging whim, brought back my interest i