"regular gas option" auto. trans.
CANADIAN ENGINES, IDENIFICATION OF ENGINES USED WITH AUTOMATIC TRASMISSIONS - All 1953 Series
The 1953 passenger car engines that are used with automatic transmissions are identified in Canadian Production by the number "9" stamped in front of the engine serial number. The starting engine serial numbers for 1953 Production engines are B-119001
When the vehicle is equipped with an automatic transmission, the figure "9" will precede the engine number. For example, Buick engine serial #B-119001 would indicate Synchro-Mesh transmission. If the vehicle was equipped with automatic transmission, the engine serial number would then be W-9119001.
This numbering system may have been used thru 1963. At some point, the letter B may have been changed to C to indicate the more powerful engines used in the bigger cars.