The 6AK5 is an amplifier pentode that is physically small and the electrode assembly is no more than a 10 mm cube. The use of this device lay in low noise RF amplification at VHF. See also5654 special quality version of the 6AK5.
Within the box shaped anode can be seen the grid structure. It is hard to see the control grid as it is made of very fine wire and close in to the cathode. It can be seen on the hi-res pic on the DVD. The screen grid is a close wound spiral of less than 0.5 mm pitch. The suppressor grid is a gentle helix some distance out from grid 2.
Looking flat on to the back of the broad face of the anode.
Philco always added this phrase to their products to increase product loyalty.
The thin glass tube envelope is 18 mm in diameter and excluding the B7G base pins, is 36 mm tall.
References: Data-sheet, 3002 & 1040. Type 6AK5 was first introduced in 1942.