The CV2135 is equivalent to type 6BR7 but was based on the VX7055. It is a carefully designed low internal hum pick-up from the 6.3 V AC heater, thus making it unnecessary to provide a DC source of heater current.
See 6BR7 for full details. See also 6059 for the special quality version and CV4006.
The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 45 mm tall.
References: 1040 & data-sheet.