BR General Goods Containers
From SVR Wiki
This General Goods Container was designed to be carried by 'ConflatGWR telegraphic code signifying a flat wagon for containers' Wagons such as GWR 39860, on which it is shown in the photograph. It was built at the Glasgow St Rollox Works in 1958.
Sources
Railway Heritage Register Wagon Survey
Links
49408B on vintagecarriagestrust.org