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.
Our other Osram DL63 has a coating inside the envelope.
The Osram brand label. The Type designation is etched into the glass on the opposite side. The oval shape of the etched information is typical M-OV.
The triode is at the top with the blackened anode. Below the mica is a bright box, this is a screen connected to the cathode. The diode anodes are the two rods. The heater is twisted into a double helix that can be seen inside the screen before it enters the cathode tube.
The classic envelope is 38 mm in diameter and, excluding the IO base pins, is 100 mm tall.
References: 1040 & 1043. Type DL63 was first introduced in 1939.