The DH107 is a double diode triode for superhet receiver applications. The three sections share a common cathode and the diodes would be used for signal and AGC detection. The triode is for voltage amplification.
The cathode tube passes through the triode at the bottom and then up between the two diode anodes, one each side of the cathode.
Each diode anode is U shaped and the triode anode is a blackened cylinder.
The diode anodes are bright and have a ridge pressed into them to confer greater rigidity.
The thin glass tube envelope is 18 mm in diameter, and excluding the B7G base pins is 46 mm tall.
References: Data-sheet & 1040. Type DH107 was first introduced in 1951.