That looks like a model ST4-B, not an ST4. That would make it either a Trac Master or a Snow Master, depending on what year it was built. I seriously doubt if it is a military unit, but it might be. A military unit would have a 24-volt electrical system (or probably some remnants of that). Military units also seem to have had the gas tank relocated but that one shows the original fuel tank position. Most military units had open cabins or full cabins, at least in Europe, not sure how many military units came to North America, but that is cleary a short enclosed cabin, not an open cabin, nor a full cabin. The headlamps are not stock, or if they are, they were taken off their mounts and reset lower directly onto the fenders. Grill and hood are clearly not original. I doubt if the mirrors are original either. I've never seen any photos of a 'military' paint job that looked like that one, so I wonder if that white/black paint is original, but I would question it. Also, on the front passenger side fender is what looks to be a stylized Swastika, that would certainly not be something that would have been used in the late-50's/60's/70's which was the "cold war" era between NATO and the East Block. The Swastika would date back to the 40's era of World War II. BTW, does it have windshield wipers or front cabin running lamps? I don't see them, but then again I have bad eyes.