Metal Envelop Triode 6C5 / 6C5GT CEI "NOS"

6C5 CEI "NOS", 6-pin, 6.3V. Made in USA

The reason type 6C5 disappeared from the lists fairly early is that it was superseded by the 6J5 which was a direct replacement. Most 6C5s were of the metal-envelope type whereas most 6J5s were 'GT/G' and therefore suitable for a wider range of applications.  The thin metal tube envelope is 25 mm in diameter and, excluding the IO base pins, is 50 mm tall. Type 6C5 was first introduced in 1936.