The CV1286 is an audio output pentode with an 18 Watt anode dissipation. The prototype was the Mullard EL35. The old service code is NR77 and this is also on the envelope.
Through the internal coating can be seen the shape of the anode.
The anode is made of mesh. The cathode tube can be seen to be oxide coated and has a reduced diameter at the top to fit into a small hole in the top mica sheet. It is a true pentode with three wire grids.
The classic envelope is 44 mm in diameter, and excluding the IO base pins is 109 mm tall.