What are the 4 steel plate boxes welded on the body for?
I went looking for the answer to this question by looking at various pictures of the M-7 online - the boxes on the front are perfectly sized for carrying spare sections of track, and perhaps that was their original purpose. I found pictures of M-7s in action with all kinds of different things in those boxes tho - packs, oil cans, sand bags, tool kits, camo netting, etc.