If you read the TM for the trailer and the TBs on field mods, it was made in a hodge-podge of variants without particular benefit of model number changes. While the intent was that each model had specific features the TM makes it pretty clear that a lot of mix-n-match changes were made for specific end uses at the manufacurer, depot and unit levels.
Some were changed to heavier running gear and re-designated as M1073(?) 7-1/2 ton trailers. That seems to have been pretty common in armor units where each battalion had (has?) several 7-1/2 ton trailers for transporting "all up powerpacks" for M1 tanks.
Some had stake pockets for bows, particularly the 100 kW generator trailers, and some had squre tubular superstructures such as the laundry trailers.
The are two bed lengths (approx. 12' and 14' from memory) Versions were made with the "A" frame front end, with the extendable straight bar for tracked vehicles and with both on the same trailer. They could have had air over hydraulic brakes, surge brakes with the bar and, according to the TM, some were made with both surge and air over hydraulic on the same trailer. That last is the only version I've never seen.
The leveling jacks are "off the shelf" commercial and they appear to have installed whatever was available at the time they built the trailer.
I've seen versions that were depot built and commercially built.
About 4-5 weeks ago there was a pallet of draw bars in a GL lot. I seem to remember that it was in VA, NC or SC but could be wrong on locaton. In fact, someone posted a picture of them asking what they were. This thread has a god title. Hopefully, a SSer bought that lot and will see it.
I'll keep me eyes open but have not yet seem M1061 or M1073 bars anywhere.
Lance
