The 20L1 from Mazda is from the early days of all glass construction in the UK. This is a low impedance amplifier double triode and could have found uses in a wide variety of equipment.
Our other 20L1 differs from this exhibit in the style of envelope lettering.
The 12.6 Volt heater requirement makes this particularly suitable for vehicle use, likewise the 200 mA current rating makes it suitable for television use. The 6L1 is identical except for a 6.3 Volt heater.
One triode seen face-on. Note the location pip on the metal skirt.
Here both triodes can be seen end on. Their construction is identical and both have the anode bulge facing outwards.
The thin glass tube envelope is 20 mm in diameter and, excluding the B8A base pins, is 53 mm tall.