The DL67 is a subminiature audio output pentode designed for hearing aid and similar uses. Electrically it is close to the DL65 but the leads are arranged in a different pattern. The data sheet places the design as originating in 1950.
The DL67 is a true pentode and all three grids can be seen. The filament is a single strand running through the centre of the grids.
The suppressor grid is an open spiral and the screen grid can be seen close to the centre. The control grid wire is so fine that it can only be seen under strong magnification. The paper label shows an Italian supplier.
The red dot indicates the location of pin one.
The thin glass tube envelope is 8 mm in diameter, and excluding the base pins is 36 mm tall.
Reference: Data-sheet. Type DL67 was first introduced in 1950. See also1950 adverts.
