Original M.W.T. Marconi Osram GU50 tube
beautiful blue light glowing

mercury vapour half wave rectifier

made in Great Britain 19th of November 1952
2V/301A  AU6  CV1072  CV1626  CV2738  DCG1.5-250  ESU101  NU16  RG1-240A  RG250/1000  VU72
The filament is a twin horseshoe of corrugated tape.

The anode is a short closed cylinder connected to, and supported by the top cap.
The GU50 was very popular as a rectifier for cinema amplifiers
Vf=4V, If=3A 
 the tube seems to be unused, or used slightly, tested NOS
the tube has Europe 4-Pin (B4, O4A) base
you will get the tube you can see at the pictures
I always send the tubes by priority registered mail with tracking number within hours after receiving payment

                                                                                                                Santic [feat. Vera Hall] – Trouble So Hard