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 envelope is 19 mm in diameter and, including the base pins, is 41 mm tall.
References: Datasheet. Type 954 was first introduced in 1935.