The LS5B from M-OV was a dull emitter valve designed for audio amplification and especially as a driver for the LS5 and LS5A. The LS5B was a medium impedance device with the design use of being a high voltage driver.
Early versions of the LS series had a top pip and a metal B4 base. Later manufacture moved to a Bakelite base and moved the pip to within the base. Our other LS5B has a shaped Bakelite base whereas this has a straight base.
This example has lost its filament, but the Type designation lettering is very clear and the name Osram is a more faint etch on the other side.
This BBC label seems to date from 1957 and indicates poor performance.
The flattened nickel anode cylinder side view. The empty filament tension spring is on the right.
The grid and the remains of the single inverted V filament. The image is deceptive as the grid wires do pass flat across the filament, the curve is vertical not horizontal.
The balloon envelope is 56 mm in diameter and, excluding the B4 base pins, is 108 mm tall.
References: 1043. Type LS5B was first introduced in 1927. See also1927 adverts.