We have few details on this triode and may have been incorrectly labelled. It has a 4.0 Volt filament and is designed for transformer coupling. The maker is Fellows Manufacturing and their brand name was Louden.
Type 410LFT is not mentioned by Tyne1047 or Thrower10031043. The label says Fellows Manufacturing Co. Ltd. and not Fellows Magneto Co. Ltd. but the style is the same. We have no data on the name change as yet.
The balloon envelope is 45 mm in diameter and, excluding the base pins, is 95 mm tall.
Absolute Maximum Operating Conditions¶
Updated November 25, 2014. shape:balloon construction:pinch type:triode age:1920.1930 base:b4 heater:4.0v pins:4 pin:1.a pin:2.g1 pin:3.f pin:4.f