A VT52 datasheet I was never able to find.
  
WORKING POINTS, SEEN FROM PUBLISHED SCHEMATICS.
(see at "schematics" on this website)

Anode-Cath  GRID   CURRENT

250V        -50      44mA  
270V        -45      45mA
350V        -60V     60,8mA
245V        -45V     30mA