As mentioned above it is folded sheet brass though this one has bearings. The axles are not perpendicular to the frame or parallel with each other so the siderods would have prevented the wheels from turning. The wheel centers are brass with set screws to retain them. The brass set screws are at an angle which would cause them to try to unscrew, one side when going forward, the other when in reverse. The axles are brass and the gear and wheel centers are an easy slip fit on them.
It is not a bad looking model though it is very light. When I get a small milling machine I will attempt to carve a replacement chassis out of a piece of brass bar stock.
