The 185BTA is a power valve with a 25 Watt anode dissipation and 5.5 Watt screen dissipation. The peak anode voltage is 10 kV. It was designed for TV Line scan output. The 185BT had a maximum peak voltage of 8 kV. In use it would be biased with a 140 Ω cathode resistor.
The anode with ceramic insulators and note the screens above the top mica and below the bottom mica.
The rounded end of the anode. The supports and side flanges are in the centre of the working faces where most of the heat is generated.
The classic envelope is 49 mm in diameter, and excluding the IO base pins is 124 mm tall.