The CV901 is a late 1930's American full wave rectifier design made in the UK by Cossor after 1945. The commercial Type designation is 7Y4 and this valve from Cossor carries both names. The Marconiphone equivalent the U149 is basically identical.
The maximum reservoir capacitor is 40 µF and the minimum series resistance, for current limiting, is not given in the literature.
The anodes stack vertically and have a small front to back dimension of 2 mm at the centre.
The bright anodes are stitched together and the cathode is not central, this allows the two anodes to be mounted with the minimum of fixings.
The Cossor identification and the 7Y4 Type.
The wide glass tube envelope is 28 mm in diameter and, excluding the B8B base pins, is 57 mm tall.
References: Data-sheet, 1040 & 1043. Type CV901 was first introduced in 1938.