Maybe they changed model numbers "just because"

AM General don't even mention a 1121

http://www.amgeneral.com/vehicles/hmmwv/expanded-capacity/vehicles

I dont think its part of the m1113 ECV family, but its certainly an odd one. My only thought is that its just an increased payload vehicle with a new designation...?

the thing that i have found dealing with a lot of them is that one has an option that the other does not. for example, a pick up style, one with a winch, maybe with a rear and front winch, four door, turtle back blah blah blah....... and then you get into the 1025, 1026and all and then they do the same thing to them. heavier syspension system but not much. they also based the numbers by what you could carry on the inside as well. maintenance truck, or a TAC truck, ambo what ever. they add all kinds of numbers and just confuse the hell out of us. i would have to dig up some TM's from the unit to figure it out or call down to our FMS shop. but i will see what i can come up with. they are already doing it to the MRAP's. RG 31, 32 and 33 and the only diff. between them is that they have some diff. electonics in them. but it is the same vehicle. all around. then add the MAX PRO's and you geet a whole other ball of wax....... will see what the shop comes up with.