Details
Octal ballast. Nominal voltage drop 49 volts at 300mA. 100-70 is the Zenith number.
Known uses include:
Acratone 137K, 138K
Admiral 6Y, 985-6Y, 986-6Y
Garod 610, 769, 7090, 7390, 7390T
Silvertone 7231, 7232
Truetone D703
Zenith 6D315, chassis 5657