Matched quad 6F6S (6Ф6С) from the manufacturer NEVZ Novosibirsk. Tubes were tested under following conditions: Uh = 6,3V, Ug1 = -16,5V, Ua = 250V, Ug2 = 250V. Tubes were designed for usage in terminal stages of low-frequency amplifiers. This is the older "figural" version of the 6F6S tubes, which are nowadays quite scarce. It is direct replacement for the american 6F6G, but also for the VT66-A and CV1911 tubes. Tubes are unused and in original boxes. Made in the end of the 50's.