RL12P35
Thanks to Stig Comstedt for the information and pictures
On this specimen the heater voltage is seen etched onto the envelope. The rating is 12.6 Volts. The Wehrmacht nomenclature stands for: R = Roehre (valve), L = Leistung (power), P = Pentode. The 35 denotes the maximum dissipation of the valve. In this case 35 Watts.
The metal skirt is also connected to the cathode.
The top cap marked B is connected to the suppresor grid. This grid is also connected to the centre base pin. On the right can be seen a third top cap. This one is a dummy and no wires pass into the envelope.
Additional type reference RS287.
The specifications, in German, can be found in the RL12P35 PDF data sheet.