Trackside Post Office W334063Walthers Part # 933 4063, p. 687 Walthers 2021 HO Scale Reference. Put your stamp of approval on this detailed Cornerstone Trackside Post Office kit, a perfect way to add essential mail and express traffic to your HO operations. Typically found next door to the main passenger station in busy cities, this model fits perfectly in steam and diesel era scenes and makes a perfect destination for WalthersProto(R) and other mail, baggage, and express cars.