![](https://coimages.sciencemuseumgroup.org.uk/50/675/large_thumbnail_1972_0141_0248__0002_.jpg)
![Osram output pentode valve, type MPT4, B5+st base](https://coimages.sciencemuseumgroup.org.uk/455/826/medium_smg00259625.jpg)
Osram output pentode valve, type MPT4, B5+st base, pinch marked MPT4, cap loose, (RMW/Y300 - McVitie Weston number), by Osram, 1930.
Osram output pentode valve, type MPT4, B5+st base, pinch marked MPT4, cap loose, (RMW/Y300 - McVitie Weston number), by Osram, 1930.