Not a prototype!
BRADLEY M4 ARMOURED COMMAND VEHICLE a.k.a. M4 'Big Box' command and control vehicle. Its a US vehicle, a command post based on the Bradley/MLRS chassis. It has the same M987 basic chassis as the M270 MLRS. It was decided in 1999 to sell the existing small number of M4’s but in 2002 the US Army took them back into service. As far as is known, there were at least 25 examples produced.
A very similar vehicle is the GBCS-H, an EW station used for Communications Intelligence, Electronic Intelligence, Electronic Support and Electronic Attack.
a.k.a. XM1010 CARRIER, FULL-TRACK, ELECTRONIC WARFARE a.k.a. EFVS [Lit: Electronic Fighting Vehicle System]