Type 8012 is a VHF/UHF transmitting triode and dates from the early 1940s and has a thoriated tungsten filament as did the earlier 1628.
The control grid can pass up to 14 mA grid current and dissipate 1.6 W. The maximum frequency of operation is in the region of 500 MHz. The 8012A is rated at full power at 500 MHz.
The side pins extend to 60 mm. The anode is connected to the set furthest from the cathode. The grid is connected to the set of pins on the left of the picture. The three base wires connect to the heater and cathode.
The evacuation seal is within a re-entrant cavity at top of the envelope.
Another example with the identification at the top. The sealing-in tube extends within the envelope and to it is fixed the getter holder. The getter has turned white suggesting that there is no vacuum. A third example has the same milky getter and that has a broken seal.
The Etched identification.
The anode seen looking directly into the pins.
The thin glass tube envelope is 25 mm in diameter and, excluding the base wires, is 92 mm tall.
References: Datasheet & 3002. Type 8012 was first introduced in 1942.