This wagon was acquired from the Admiralty at Rosyth, and was probably rebuilt there. It has Glasgow & South Western Railway type end tipping doors, but other components are from the North British Railway.
The either-end doors are a typical G&SWR feature - the lack of wagon turning facilities at Troon Harbour meant that coal wagons unloaded there had to be capable of being tipped at either end. (The railway had massive infrastructure for wagon handling - one reason why wagon sizes remained fixed from the 1870s onwards.)
Since the wagon has 'NBR' cast on its grease axleboxes, it has been painted for display as a North British Railway wagon. The Loco Coal livery, and the running number, are not original.