These railcars were placed into service between 1948 and 1953. They were numbered RM 20 to RM 35. They were built by Martin & King under licence to Walkers Ltd, England.
The units featured an engine/power bogie cab unit to which a trailer cab unit was attached.
In 1954, a power unit only was built. This was RM 35. It seems to have been used a power unit replacement when other units required maintenance.
The railcars were out of service by the mid 1980's.