The FER1 is a directly heated audio triode from the 1920's. The filament is a dull emitter thoriated tungsten wire. The internal construction is obscured but the diagram on the box indicates a spiral wire anode.
The label informs that the filament is to be run at 4.0 Volts and will consume 0.1 Amp. The anode is designed for operation at 40 - 80 Volts. The base is B4 with simple split pins. The FER1 was designated for service as a detector and AF amplifier.
The box identifies the manufacturer as Fellows Magneto Company a British company, based in London, that marketed the valve in 1925. The brand name was Louden. The price of 12 Shillings shows how expensive valves were. At the time the average wage was of the order of 40/- (Shillings) a week.
In keeping with the BBC requirement the box proudly declares that the valve is all British, including capital. I wonder if this is a dig at Mullard with its Dutch partner Philips.
Many thanks to Simon Balderson for donating these images and valve details.
The balloon envelope is 46 mm in diameter, and excluding the B4 base pins is 97 mm tall.
Reference: 1003. Type FER1 was first introduced in 1925.