The Mazda AC/SG is and AC heated Screen Grid or tetrode amplifier for RF use. Our other AC/SG has a different construction and shows how the box screen moved to a helical grid.
The heater is the then UK standard of 4.0 Volts at 1.0 Amp. The original valves in 1929 had a metal top cap as can be seen in the advert. The screw top cap style of this exhibit is later and the top-hat top cap arrived in the mid 1930's. Thus this valve looks to date from 1932 or just after. Performance was increased in 1932 and the characteristics presented are for the enhanced version. The main change was a doubling of the AC anode resistance. A similar performance enhancement was applied to the DC/SG that first appeared in 1931.