The GWR introduced an 8t ballast carrying open wagon made of steel in the 1890s and, with a change in the side door arrangement and increase to 10t payload a substantially similar wagon was built until 1949. Some internal users in the collection. Officially known as 'Starfish' I have never seen this branding used. The CO mark dates back to at least 1929 on the GWR and means vehicles under the control of the Chief Office.