Vacuum Tube - 12SQ7, Diode, Dual, Triode
New-Old-Stock (NOS) tube.
The 12SQ7 combines two diode units and a high-mu triode in a single envelope. Each section uses a common cathode. It is intended for service as a combined detector, AVC source, and high gain audio amplifier.
Also known by US military identifier VT-104.