The standard Philips/Mullard naming convention would name this UHF pentode as EF180, but for special quality valves, such as this, the numbers are presented after the indication of the heater. E = 6.3 volts.
The E180F is a high-μ RF pentode primarily intended for use in wideband amplifiers in telephone carrier systems, radar equipment and measuring equipment.
These valves would be used for the front end amplification stage of high quality receivers up to the UHF region of the spectrum.
It can be seen that in this miniature envelope is an even smaller valve, this very small size helps to reduce inter electrode capacitances and thereby raises the maximum usable frequency that the device can operate at.
There are screens top and bottom. The thick mica discs resist the effects of vibration for aircraft etc. applications.
The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 36 mm tall.
References: Data-sheet & 1040. Type E180F was first introduced in 1955.