The 5876A is a microwave disc seal triode. The device is physically small, coaxially designed and connections are brought out to connections along the body of the valve so as to better locate the valve within a resonant cavity. The cathode connection is made via a spring clip that fits over the metal body.
The valve is rated for high altitude use and for use as a Class C amplifier and oscillator at up to 3.0 GHz.
The 20mm diameter grid connection ring. The red caps are protection during storage and transit.
The heater connections exit from the base. The cathode connects to the silver-plated tube.
The evacuation seal on the left. The copper anode has the grid cage passing within it.
A closer view of the end of the copper anode with the grid cage passing into it. The vertical wires have a fine wire wound round them to form the grid.
The thin metal tube envelope is 6.3 mm in diameter and, excluding the base pins, is 54 mm tall.
References: Datasheet & 4038. Type 5876A was first introduced in 1964.