The DL2 is a battery output pentode on a Ct8 base. The lettering is damaged and difficult to read on this exhibit. We also have the DL1 also from 1939 but with a smaller output.
The rounded bright anode and long connections to the pinch and base. The two mica sheets are 20 mm apart.
The top mica components. One filament tension spring is in place and the other is raised showing that the filament is broken.
Mark from Vintage-parts sent this image with better lettering.
The wide glass tube envelope is 30 mm in diameter, and excluding the Ct8 base pins is 82 mm tall.
Reference: 1043. Type DL2 was first introduced in 1939. See also1939 adverts.