The X593 is a 1000 watt experimental tetrode. The first example is dated March 1957 (C7). The second example is an "R" revision dated July 1957. It is an experimental version of the 4CX1000A. This tube is longer than the 4CX1000A and has a domed cap. The first tubes made were with a 7 volt filament. Begining with the "R" revision they became 6 volt. The first tube came with a X667 socket which was designed for it. Several revisions for the X593 and X667 were made.
Length = 4.87" Diameter = 3.35"
Max voltage = 3000
Max current = 1 amp
Fil voltage = 6 or 7
Fil current =