The CV15 is a directly heated triode with a thoriated tungsten filament. The envelope features a copper to glass seal and operating frequency is up to 300 MHz. The prototype was the experimental type E1266.
Thanks to Jonathan Friedman for sending the images.
The CV15 is printed on the brass base.
A closer view of the brass base with mounting holes.
The other side of the base block has an arrow and what looks like a V followed by a P.
The grid connects to the left hand cap and the filament leads are to the right. The anode is in the centre connected to the brass block.
The filament leads entering the anode.
The wide glass tube envelope is 25 mm in diameter, and excluding the base pins is 185 mm tall.