This one is 3-wheeled, with rear wheel steering, smaller than normal diameter wheels, and no windshield so to be able to fit under the wings. It was also quite nimble on carriers. Built by O.E. Szekely Associates, Philadelphia.
E-Willys added in the comments, just now, " the jeep community was under the impression that only O. E. Szekely manufactured APUs. Since that time, Nick Oxender discovered an APU that proved there was a second producer of APU jeeps: Valentine Welder and Co. It manufactured a four-wheeled version with the f-head motor and classic APU triangular hood bump. There is no evidence Valentine ever manufactured a 3-wheeled version. Earlier this week Nick listed his Valentine APU, the only one known to exist out of 75 made, on eBay, but it didn't break his reserve price."
1950, July 4th, on the Valley Forge