Vacuum Tube - 6K8, Triode, Hexode
New-Old-Stock (NOS) tube.
Also known by US military identifier VT-167.
The 6K8 consists of a triode oscillator and a hexode mixer in a common envelope. The physical design of this tube reduces interaction between the oscillator and mixer sections and makes for stable operation in superheterodyne receivers on the high frequencies as well as the broadcast band.