The RV12P3000 is a miniature pentode for audio output or RF up to 100 MHz. The anode dissipation is 6 Watts.
Kriegsmarine was the navy branch of the Wehrmacht, the German armed forces from 1933 to 1945.
The anode is in two halves joined by a strap. Inside all three wire grids can be seen.
A closer view of the grids.
The eight pin base was a push fit into the valve holder. The thread in the centre would originally had a small handle fitted to allow the valve to be pushed into the socket. SeeRV12P2000 for an example of the handle.
The control grid has a heat radiating fin at the top. In essence the valve is of all glass construction with the lead wires connected to the side contacts. Unlike the acorn valves the pins are embedded in the Bakelite base and do not stress the glass envelope.
The wide glass tube envelope is 26 mm in diameter and, excluding the base pins, is 62 mm tall.
Reference: Datasheet. Type RV12P3000 was first introduced in 1943.