Hi sewelja,
First welcome to the board.
The hull might be one that was used on an M4 105mm.
I never understood why the M-4 late used the composite hull but looking through the Hunnicutt book I've seen pictires of M4's that used the M-4-A3 car body, but had the 105mm mounted in the turret.
Not sure that this is the answer, but hope it may give you a clue as to what to search for or maybe provide a lead that some one else can follow through on and help you out.
Regards,
Joe
Just remember, ignorance is no excuse for the law. - Moe