Osram Catkin tetrode valve, type MS4B, B5 base, no screening can, with top terminal, marked dummy, (RMW/G64 - McVitie Weston number), by Osram, c. 1933.
Osram Catkin tetrode valve, type MS4B, B5 base, no screening can, with top terminal, marked dummy, (RMW/G64 - McVitie Weston number), by Osram, c. 1933.