These were the 1st class sitting cars for the original broad gauge Spirit of Progress. Further building after the SOP started running saw the class grow to 16. None of the AS cars were converted to SG when the Spirit of Progress was converted to standard gauge in 1962. The class remained on Broad Gauge providing first class air conditioned service on longer distance trains.
In the mid 50’s 3 AS cars were converted to ABS cars , 2 of these cars were subsequently converted to mini buffet cars. In the early 80’s the remaining AS cars were recoded to BS
Brown & Cream with brown painted window arches