The DH81 from Osram is a double diode triode first seen at the 1947 National Radio Exhibition. The design use was as detector, AGC rectifier and first audio voltage amplifier in broadcast superhet receivers and effectively was the 6Q7GT on the new B8B or Loctal base. Type DH81 was obsolescent by early 1951. The DL82 was similar and pin compatible but had a lower amplification factor and a vari-μ characteristic.
The Marconi label.
The screen around the bright anodes of the signal diodes.
The signal diode anodes form complete cylinders around the common cathode.
The triode section.
The wide glass tube envelope is 32 mm in diameter, and excluding the B8B base pins is 56 mm tall.
References: 1040 & 4018. Type DH81 was first introduced in 1947. See also1947 adverts.