Ever Ready and Lissen
Lissen bought in valves without bases and added their own. It’s not clear if ANY early Lissen valve wasn’t bought in. In 1928 Ever Ready bought control. By 1935 Noah Cole the founder of Lissen was gone as he had founded Vidor in 1934.
Ever Ready adopted a continental style scheme and from 1935 bought Mullard valves (or possibly some were really made by Philips in Netherlands) but used their own continental style scheme
A = 4V (usually indirect, but not always)
C = 200mA series indirect, any voltage.
K = 2V (usually direct battery filament)
S= 4V (Usually direct)
Next digit is number of electrodes. i.e. 2 = Diode, 8 = Octode, though Pentodes are 7. If it’s a single device, then second digit is zero. If a dual device such as TDD13C, then 2nd digit is different device C23B, the “3” indicates a Triode. Thus K33A is a dual 2V Triode and K77B is a Dual 2V direct pentode.
The suffix letter indicates a later version, or for battery types selected matching bias; for Push Pull, or Screen grid bias tap to use.
All the All Dry valves (1.4V) using Ever Ready Branding used Mullard type numbers. Mullard used US numbers 1938 to 1946 for US imports they resold. In 1945 the late 1930s 5 pin and 7 pin 2 volt valves (Ever Ready K series) had Octal bases fitted as there was a market still for Accumulator fed LT (no home Electricity and cheaper than All Dry LT batteries if a nearby cycle shop or neighbour to charge the cell). The 2 Volt valves thus in radios sold up to 1950. But Ever Ready being a Battery maker sold no sets using 2V LT after 1939. Only one post 1942 Ever Ready set even had a mains option, the 1956 BEREC Fiesta.
From Mullard Valve Guides
Usually AC parallel 4V (Mostly Indirect)
All AC/DC series 200mA (All indirect)
All DC battery parallel Direct 2V (Lead Acid Cell)
Usually Mains 4V Direct