Details
New old stock 9 pin miniature triode pentode. Various brands. "A" has controlled heater warmup time.
NSN/FSN = 5960000820039, 5960003004969, 5960004188729 (aged), 5960005396350, 5960005561476, 5960006068708, 5960008124394, 5960008390856, 5960009858986, 5960010895448, 5960011115141
HP/Agilent Number = 1933-0001, 5080-0412 (aged)
Tektronix Number = 154-0078-00