This wagon is a low machinery-carrying wagon known by the codename 'Lowmac MU'. With a wheelbase of 25'6", it has a low centre deck (only 15.25 inches above rail level and 15 feet long) with ramps at both ends. This enabled heavy equipment with wheels or tracks to be loaded over the ends and to be carried within the height limit, known in the railway industry as 'loading gauge'. Designed for revenue (commercial) traffic, typical loads were an earth mover, road roller or small lorry.
B904134 was built to BR diagram 2/250, the last one of a lot of twelve (lot No. 2976) built at Swindon Works in 1957. It is fitted with vacuum braking, reflecting the contemporary policy of British Railways.
The 'M' in the code 'Lowmac MU' indicated that the vehicle was ordered for the London Midland Region, the 'U' being its order in that Region's diagram book. However, the design has its parentage in older GWR 'Loriot' wagons.
Arriving on the Bluebell on 13 June 1977, it was acquired to assist with engineering work, transporting plant to worksites on the single line, but also for its historic interest.
