MH4, MARCONI OSRAM, TRIODE, AIR MINISTRY, 10E/9594, WARTIME PRODUCTION, 1MTL, AC/HL, AR17, CV399, CV1037, D4, HL4, MH4K, NR31, VR37 Beautiful screeded broad ST19 bulb, black base, today we have a Marconi Osram MH4 with an elliptical bicolour Osram decal to the obverse. The device has been tested using our VCM163 valve tester and shows good emission.
