An old russian tank, It was a 4×4 light armoured car, employed by the Soviet Army from 1942 into the early 1960s (http://en.wikipedia.org/wiki/BA-64)
A good model, but you really gotta make your vertex density more even. The contrast in polycount between the hatches and wheels and the rest of the model is just insane, those have a LOT of unnecessary vertices.
You are right.
I realized that when the exported .obj file was about 60MB (actually I had to insanely "Remove doubles" with a big threshold to be able to upload to p3d.in, but some glitches appeared so I uploaded the original .blend here)
Anyway, working on it.
Seconded what snipperbes said. The tires look like they had a re-mesh modifier put on them, and now have some uneven edges. Maybe that was intentional? Still, could be done with way fewer verts.