These carriages were originally built at Doncaster for use as excursion stock. Separate guard’s and luggage accommodation was provided, the latter carrying 2 tons. The only difference between the two diagrams is the original provision of B1 (D183) or Commonwealth (D184) bogies. In 1980/81, four D183 and 14 D184 were converted to micro-buffets. The only external evidence was the addition of the MICRO-BUFFET legend in one window.