The CV455 is a VHF double triode, useful for RF stages, oscillators and frequency multipliers. The commercial type designation is ECC81. The American 12AT7 was the prototype.
The interesting point to this exhibit is that it was made during the cold war in the GDR (East Germany) then part of the Warsaw Pact but with the British CV designation as used by NATO.
There is bold lettering on the glass but we are not sure waht is says.
The anodes are folded and stitched on one side, making an asymmetric design.
The two triode sections with the screen between.
The thin glass tube envelope is 21 mm in diameter and, excluding the B9A base pins, is 48 mm tall.
References: Data-sheet & 1040.