The AP412LF is a bi-grid valve designed for audio. The Aneloy AP412 valves were the HF, P, RC, SC and U all were bi-grid valves.
Thanks to Richard Stibbons for donating this valve.
The LF designation is also present on the pinch as well as being etched into the envelope. The side contact is for the second grid.
The B4 Base has simple split pins. The side terminal is probably original.
The filament is broken. On the right of the anode are the two grids the inner is made of thinner wire. The construction style is close to that of the Cosmos Shortpath valves.
Both grids are fixed on one side only to thick wire supports.
A better view of the grids.
The balloon envelope is 35 mm in diameter, and excluding the B4 base pins is 98 mm tall.
Reference: 1043. Type AP412LF was first introduced in 1927. See also1927 adverts.
