The first 25 production Supercharged 4½ Litre cars where Chassis Nos. SM3901-SM3925, all with "smooth-case" blowers. The next 25 were Chassis Nos. MS3926-MS3950 and had "rib-case" blowers.

Production Blower Bentleys had handbrake handles made from rectangular stainless steel, whereas the five 4½ litre race cars for Tim Birkin had the "H" section handle, but were drilled for lightness.