GWR goods stock which ran in passenger trains was painted all over brown, as a compromise between ordinary freight stock grey and the chocoloate and cream of passenger coaches. The "Brown Stock" included a variety of types, such as horse boxes, carriage trucks, fish trucks and the various "Siphons", used mostly for carrying milk.

The Brown Stock followed the general changes in the sizes of letters used on ordinary freight stock, with 25 inch letters introduced from around 1903, replaced in 1920 with the 16inch letters. 1934 saw the GWR roundel introduced, which seemed to fit this type of vehicles far better than it did the passenger coaches. Later, the small letters were used on the lower left side, as with ordinary goods stock.

Some Browns also carried the appropriate telegraphic codes, written in block letters at the center of the sides. Special instructions, such as "For Fish Traffic Only" were in italics.

The six-wheel Siphon seen here is to Diagram O4, built from a Slaters 7mm kit. The open-slatted sides had a cooling effect on the milk churns carried.