In 1972/1973 thirty three cars were modified from ABU_ which were cars with both First and Second Class compartments.
Car numbers were:
2 - 6, 8, 9, 11 - 14, 16, 18 - 20
22, 24, 27 - 30, 33 - 35, 37, 39 - 47
In 1981, the Bright Historical Society purchased BU 37. However it was later found to be in poor condition. To allow for the purchase of the nominated car, BU 20 was renumbered to BU 37 and the car disposed transferred to Bright. The original BU 37 was renumbered to BU 20 and scrapped.
Similar to cars built in the 1910 to 1914 era, these cars were fitted with "divided windows"; a split window frame that allowed the upper portion to raised without letting the flow of air 'gust' the compartment. These windows were made unuseable in the late 1930's.