The Moorhead series D (D. to avoid confusion with Type D) triode dates from 1920 but the original design of electron relay is earlier. Patent problems existed and RCA licensed Moorhead in 1921 to make a limited number of Tubes. This number was completed in 1922.
The date information for this valve comes from the attached label.
The anode is a bright plate 18 mm across and folded at the top. The grid is wound on glass supports that are integral with the pinch.
The structure can be seen to include the glass grid support piercing the anode to give the anode a top support.
The grid and anode end on.
The filament is a single inverted V and has corrugations that may be there to compensate for length variation when hot.
A better view of the filament.
The Bakelite base with brass connections.
The wide glass tube envelope is 26 mm in diameter, and including the base is 116 mm tall.
Reference: 1047. Type D. was first introduced in 1919.
Updated December06, 2018. shape:wide.glass.tube construction:pinch type:triode age:pre.1920 base: pin: