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. This example has a shaped base and is probably earlier than the LS5B with the straight base.
Our example has lost its filament, all its markings and the base is loose. The only visible marking is the B written on the pinch. The anode is a flattened bright Nickel tube, the grid is shaped in the same oval as the anode whilst the filament would have been a single inverted V of Thoriated Tungsten.
The filament tension arm is clearly seen in the above picture.
Seen from the top the pitch and form of the grid is visible as is the junction between the main filament support and the final length of spring steel used as the tension arm.
Although not easy to read the marking on the base around the central hole is M-OV and probably a date code.
The balloon envelope is 53 mm in diameter and, excluding the B4 base pins, is 111 mm tall.
References: 1043. Type LS5B was first introduced in 1927.