The Cossor Point One Det & LF is described on its black paper label as designed for rectification (signal detection of AM signals) and low frequency amplification.
The electrodes are partially obscured. The basic operating details are on the paper label.
It is possible to make out the shape of the anode. It is similar to that introduced with the W3.
The Cossor Point One range of 1927 preceded the later unified range when the name changed to 210LF.
The balloon envelope is 42 mm in diameter and, excluding the B4 base pins, is 87 mm tall.
References: Data-sheet, 1043 & 1040. Type Point One - Det & LF was first introduced in 1927. See also1927 adverts.