Vintage genuine British made 3A/172B HL1320 CV1670 STC and ITT triode amplifier tubes. These are all made in the same factory (ITT took over from STC in the late 70's).
3A/172B is a medium gain (mu = 30), triode signal tube with a B7 British base. For more information, see data sheet : http://tubedata.tubes.se/sheets/146/h/HL1320.pdf
Tubes are tested with an AVO tester and test within normal factory tolerance for plate current and transconductance, and are tested for leakage and shorts.