Although Amal have claimed since the war that the 276 was a 1939 introduction and this was the first date that it appeared in their printed lists (for WD Norton and BSA "Export" models), Norton literature, period photographs and indeed Amal's own assembly cards (copies of which are in the VMCC library) confirm that the 276 was in use from 1936.
This was of course the "Norton" type with the flat on the jet block with two small airways and not the "R" with one large central airway. The "R" would indeed have been a 1939 introduction for BSA.
Most 1936 WD Nortons were fitted with large air filters next to the rear wheel and the 276 was developed for them. It's a different casting and lacks the "gusset" under the inlet which allowed the "R" type central airway to be bored. These must be very uncommon instruments today. Perhaps produced for a few thousand WD Nortons from 1936 to 1938. Indeed, most Type 76 mixing chambers have the gusset indicating 1939-on production as Amal logically switched to a universal casting.
