The UC92 is a triode that is designed for oscillator or mixer use in AM/FM broadcast receivers. The UC92 is directly heated and for its intended use hum pick-up is not an issue.
The anode cavity has a front to back dimension of less than 2 mm.
Seen from the side it can be seen that the plate formed into the anode is made wider than required so as to add additional cooling. The 8.5 mA anode rating was designed for low noise amplification at the expense of increased dissipation.
The thin glass tube envelope is 18 mm in diameter, and excluding the B7G base pins is 45 mm tall.
References: Datasheet, 3002 & 1040. Type UC92 was first introduced in 1952.