The DL63 double diode triode by Osram would have been designed for receiver applications. Traditionally such a valve would provide signal and AGC rectification, followed by the first audio amplification.
The paper Marconi label as well as the Type designation in the typical M-OV lozenge as seen in the main image above.
The triode section with blackened anode. Below the central mica can be seen the screen that shields the diode anodes.
The classic envelope is 38 mm in diameter and, excluding the IO base pins, is 96 mm tall.
References: 1040 & 1043. Type DL63 was first introduced in 1939.