Details
New old stock 9 pin miniature pentode. Various brands. Type 6677 is selected for mobile service (steady output at 6.3V +/- 1.3V on the filament).
NSN/FSN = 5960002642999, 5960002958464, 5960004335430, 5960006150243, 5960007131921, 5960007150190 (6677), 5960008020520 (6677), 5960009127536, 5960010657058, 5960010923562, 5960011280745
HP/Agilent Number = 1923-0012, 1923-0030, 1923--0066, 1923-0072. 5080-0407
Tektronix Number = 154-0031-00, 154-0286-00