The 527 is a 300 watt triode with a mu of 38 that was produced late in WWII for use as a pulsed oscillator in the SK-1M and SR high power search radars. The first example was made in May 1945. Full ratings to 200 MHz. Four tubes in a ring oscillator produced a pulsed output of 1,000,000 watts. Penta Labs began business after EIMAC gave them the rights to produce this tube in the 1950s. They renamed it the PL-185 and this example was made for the U.S. Navy.
Length = 12.00" Diameter = 4.00"
Max voltage = 20,000
Max current = 160 ma average
Fil voltage = 5.5
Fil current = 135 amps