The wagon I am working on is 10T Covered wagon with a 10ft wheel base diagram 1812 Manufactured by the Metropolitan RC & W Company in 1912 (batch of fifty) Order Number B1771. Now the 8T looks interesting as 15ft 6in = 108.5 mm and I have a max size of 115mm, may be the second wagon to come in the Sassanach range Paul
Indeed corrected and well spotted Paul, covered van NSR 5427 was built by Metropolitan Amalgamated Railway Carriage and Wagon of Saltley Birmingham ... same company who later built two 30 ton bogie rail trolley wagons for NSR in 1921.