As "aksnocat" points out, that is a Snow Master version of the Snow Trac. It has longer tracks (one extra bogey wheel) and wider tracks (5 belts instead of 3). The Snow Masters came in several configurations. This one is a tall cab (which means it is probably a newer unit) with a few extra inches of headroom. It also has full width side fenders that run all the way to the back, other versions had full width fenders only in the front but they tapered to standard width near the front of the cabin. This also has the optional rear extentions over the rear of the tracks to help keep the snow from piling up on the back of the machine. A Snow Trac's tracks do not extend past the back of the cabin, but on this Snow Master you can clearly see the tracks extend beyond the rear of the cabin and that is the reason for the rear extentions.
Lyndon's Snow Master, which was recently sold to Mtntopper, is a very similar version of this unit.