[Milsurplus] When Were Metal Case Tubes First Produced?

[Unserviceable but Repairable]

There's a tenth 1st production metal tube.  It found home in a 6F6-style 
envelope & was named 6D5.  Basically a type 45 with a 6.3V filament & made
no sales progress.  Bit more info in L. Sibley's Tube Lore

Loaned one to a pal years back.  Pal died & so did the 6D5

Wud like another again

  Marty