The 954 miniature all glass acorn valve is a pentode with a 6.3 Volt heater. Visual inspection shows the three grids within the anode cavity. In 1943 in America the 954 was re-worked onto the B7G base and issued as the 9001.
The normal 5 side pins are supplemented by pins top (a) and bottom (g1) making seven contacts in all.
The small size of these valve enabled them to operate at VHF.
The valve is marked JRC954, the JRC marking being a US Government quality code.
The RCA logo and lower shield.
The main horizontal pins sealed into a thickened ring of glass. The pushing down on the valve to get the five pins into the slots in the special base would often crack the glass and thus ruin the valve.
The wire grids can be seen through the gap in the anode. The anode connection is on the right with the base connection at the other end going to the control grid.
Another view. The control grid is wound on copper supports.
The acorn envelope is 13 mm in diameter and, including the base pins, is 44 mm tall.
References: Data-sheet. Type 954 was first introduced in 1935.