Some of our sources suggest that the CV5281 does not have a direct commercial equivalent, however, the ECC84 is given as sensibly equivalent and the data given here is for the ECC84.
The maker's name is not present but the font is typically that employed by Mullard.
It is a pair of triodes separated by a screen and designed as a cascode amplifier for use in VHF receiver applications. The triodes are independent with separate cathode connections. The ridges on the top of the envelope suggest that this valve was made on a Mullard-Philips production line.
Face view of one triode with the screen behind.
Here the shape of the box anode is clearly seen.
The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 47 mm tall.