Here we have the other ONE of a pair of MARCONI U52 valves, new; never used with original Swedish government bulk packaging.  This listing is for one tube.

MADE IN ENGLAND

      Vintage 40's New Old Stock

   CV1071 / 5U4G / U52  Full-wave rectifier tube.  

M.T.W.:  MARCONI'S WIRELESS TELEGRAPH CO.LTD. CHELMSFORD, ENGLAND

● INVERTED POT getter 

●  BEAUTIFUL  smooth BLACK plates  

The pictures are worth a thousand words; please see actual pictures of this tube.

Guaranteed NOS and to perform as such!  It is  described in detail at www.head-fi.org:

Dubstep Girl's Massive 5AR4/5R4/5U4G Rectifier Review/Comparison! (Rectifer Tube Rolling thread)

GEC U52/5U4G/CV575 (Brown base)

British tube made by GEC/MWT/Marconi/Osram, etc. I've also seen it branded under Mullard or Brimar. It should be compatible with most 5U4G amps (I have confirmed compatible with Woo WA22 and Stratus).  Mine has grey plates but I've also seen black plates as well as black base versions of this tube. Compared to the Western Electric 422A, I think this would be the second best rectifier tube available. Performance is almost the same as the Western Electric 422A, perhaps only being a little warmer and having a more euphonic tone/timbre/decay. However, it maintains its speed, transparency, layering, soundstage, and imaging. Like the WE422A, it's pretty much nearly perfect in every way and maintains a sort of neutrality throughout. Warm tube sound but with extended air and treble, great staging, deep bass extension, very nice texture and decay as well. Absolutely zero grain with this tube, just like the WE422A, one of the best tubes out there! Sound-wise, it's very similar and shares the same British tone and sound signature of the GEC 6AS7G power tubes. Great synergy with Sennheiser HD 800. Just like the WE422A, this tube can really bring you to tears on the right music, so much magic in the sound of legendary tubes. Price is slightly cheaper than the 422A but similarly priced with tubes going for $350-500$ a piece.

Please see the pictures; Ebay's seller listing form was designed by an idiot, so just know that POSTAGE WORLDWIDE  is 25 USD. Thank you for looking.