Vintage genuine British made STC and ITT CV1653 3A/108A triode amplifier tubes in the original boxes. These are all made in the same factory (ITT took over from STC in the late 70's)
3A/108A is a medium gain (mu = 30), triode signal tube similar to US type 30 (2 volt filament) but with a different base. For more information, see data sheet :http://scottbecker.net/tube/sheets/144/3/3A-108A.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.