The 6084 (also known as E80F) is a special quality valve with a life longer than 10,000 hours. It was designed for audio amplifier use, normally in RC coupled designs. It is also specified for electrometer applications and the operating conditions are shown in the second set of parameters. In this application the input current to g1 is less than 0.1 nanoA.
This example is branded Pinnacle and is of non UK origin and so is labeled foreign.
The three wire grids can be seen through the notch in the anode. Note the gold plated pins for this professional valve.
The anode above the lower mica and screening plates below the mica disc.
The thin glass tube envelope is 20 mm diameter and excluding the B9A base pins stands 58 mm high.
Reference: Datasheet. Type 6084 was first introduced in 1951.