The 5B/254G is a 5B/254M with flying leads for direct soldering into circuit.
This family of miniature beam tetrodes was designed to have the same ratings as the classic 807. The difference in size between the 807 and this valve shows the extent to which valve technology matured during WWII and the effect of the introduction of the pressed glass base. This particular base was the earliest to be developed with eight equi-spaced pins and an external metal collar to hide the envelope seal and provide a locating spigot.
Electrically the valve is also very similar to the STC 5B/251M and electrically identical to the 5B/255M. The latter has the anode connected at the base and one less connection to the cathode.
The hard glass foot with the leads integrated into the base. The spigot covers the evacuation pip and the key ensures the correct orientation in the socket. The depression at the end of the spigot is to grip the retaining spring in the valve holder. When introduced in 1938 by Sylvania this base was called Loctal.
The lower components including the comprehensive screening needed for this RF power valve.
The top mica with anode connection to the top cap and heat radiating fins on the screen grid.
The wide glass tube envelope is 29 mm in diameter and, excluding the B8B base pins, is 85 mm tall.
