The LN309 is a television triode output pentode. It produces enough output power at 2.2 Watts for an average domestic room but was designed primarily for the frame timebase stage. It was first advertised in 1953.
In the envelope the two electrode systems are side by side.
Another M-OV sample in the collection shows a slightly different appearance.
This valve is badged with the Osram trade name.
The thin glass tube envelope is 20 mm in diameter and excluding the B9A base pins, is 47 mm tall.
References: Datasheet & 1040. Type LN309 was first introduced in 1953.