Here is a Marx prewar O gauge 6 inch #552 Rock Island green gondola with red interior, white lettering and red details.  This one is a bit rough, with some light playwear, but very presentable.  It is on a black frame.  It has 8 stamped metal wheels on metal axles, and those prewar only "Oneway" post and pincers style couplers.  The post on this one is diecast metal (they also had stamped steel ones).  All 8 of the little separate journal boxes are also still present on the side frames; the spring on the coupler is present. Photos from all 6 sides, with a yardstick in the shots for size reference.  Priced to sell, with only actual USPS Ground Advantage or Priority shipping charged!