Small Scale Military Headquarters

OK I bought the BBI M-1 on clearance it was cheap so I figured what the hey.
Couple questions on it. Would the M-1's track stay more or less the black color it comes in (its the desert sand one). Next is what exactly is the box like object that they have you put on the right rear of the tank over the taillight? and do I need to have it on for the desert version? I like the looks with out it on personally any answers would be appreciated.

I was wondering what that box is also that you attach to the rear of the BBI Abrams. Neat looking part, I just don't know what it is.

Maybe A cooler to hold the cold beer?

The only box that I know of that was mounted on the back of an Abrams is the Auxiliary Power Unit (APU). M1s, M1A1s and M1A2s had it, but newly upgraded M1A2 SEPs do not.

Thanks ChairmanMilo after that info I went and looked it up online and it does look like that is it. They were either mounted to the rear like BBI's or on the turret bustle. So one question down more to come I hope.