As has been pointed out above, it's an M101 3/4 ton trailer. Originally the main tow vehicle was a Dodge M37 3/4 ton 4x4 cargo truck, sometimes called a weapons carrier. For this reason the M101 and M101A1 shares the same wheel and tire as the M37 (5-lug Budd rims with 900x16 tires).
Payload is 1500 lbs cross-country (mil-speak for "off road"), and 2250 lbs on highway.
Gross weight on the wheels is 2640 cross country, 3360 highway.
Empty weight on the wheels is 1225 lbs.
Weight on the landing leg or tongue is 115 lbs empty, 200 cross country gross, 230 highway gross.
From the photo, it looks like there is a handbrake just barely visible behind the spare tire mounted on the front of the trailer. The M101 had the handbrakes inboard of the angled frame rails. The M101A1 had the handbrakes outboard of the frame rails. There is a minor difference between early and late M101 handbrake setups, though. It appears this is a late M101.
The parking brakes are also different. There are three different brakes originally used on these trailers. M101 early, M101 late (which should be this trailer, notwithstanding axle or hub swaps), and M101A1.
Original wiring harnesses and intervehicular cables are also different, but in this case there are only two versions - early M101, while the late M101 & M101A1 are the same.
During the 1960's, the M101 was also towed by the M715 series of 4x4 trucks. These had incompatible rims and tires, requiring a spare to be carried. Usually a spare was tossed into the towing vehicle, but some units bolted spares to the trailers.
There are also M101A2 versions. These came out in the 1970's when the CUCV's were issued. These differed in having CUCV rims and tires, and almost always a hydraulic brake actuator assembly on the nose of the trailer. This was the only version that had road brakes. All the other versions had parking brakes only.
Originally, the M101 series had wooden cargo slat sides (milspeak is cargo rack) that fit above the sides, front and doors, and hoops for a canvas top.
These trailers are fairly large, roughly being the equivalent of making a trailer out of a full sized short bed pickup, though much beefier. They would not be a good choice for an FJ40 sized vehicle. An ideal tow vehicle would be a 3/4-ton full size pickup truck. Full sized Suburbans, Broncos and vans have towed them without problems. The main issue is that there are no brakes, so 1/2 ton brakes are a drawback in hilly country with heavy loads. These are the largest *practical* trailers for most people with full sized pickups. The M104 & M105 1-1/2 ton trailers are simply too large and heavy, having been built for 2-1/2 ton 6x6 trucks. A friend does own an M105 equipped with a 375 gallon water tank and fire pump, which is used for fire protection on jobsites in the woods. He hauls it with his F-350, and it's quite a load on logging roads. He also parks it at a job site, not at home. Generally the large M104 & M105 trailers are cheaper than the smaller M101 trailers. There's a reason for this. The M101 is practical. The M104 & M105 are not, and are thus less desirable to most people.
Anyone who owns an M101 3/4 ton trailer should try and obtain an original or copy of the tech manual:
TM 9-2330-202-14P
OPERATOR, ORGANIZATIONAL AND FIELD MAINTENANCE
INSTRUCTIONS, REPAIR PARTS AND SPECIAL TOOLS
FOR
TRAILER, CARGO: 3/4-TON, 2-WHEEL
M101 (2330-738-9509) AND M101A1
(2330-898-6779)
CHASSIS: TRAILER: 3/4-TON, 2-WHEEL
M116 (2330-542-5987) AND
M116A1 (2330-898-6780)
(The M116 is a chassis without body, for mounting generators, etc.)
This leads me to think maybe this is a 1 1/2 ton rather than a 3/4 ton? What are thoughts out there on 1 1/2 tons behind the cruiser?
