The 6927 / CV2798 is a VHF double beam tetrode. It is better known as the Mullard QQV03-10. For UK Government service it was issued a CV number and thus an open specification so that it could be made by a range of suppliers.
This valve type was much used for mobile VHF transmitters, as well as drivers for the larger power valves, such as the QQV03-20A and QQV06-40A. The Amateur radio VHF AM transceiver the TW Communicator used a QQV03-10 as the PA modulated by a pair of EL84s in push pull.
The construction uses a central cathode and heater assembly together with a common screen grid. The control grids are single sided.
The reverse with an unknown mark printed on it.
The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 69 mm tall.
References: Data-sheet & 1040. Type 6927 was first introduced in 1955. See also1955 adverts.