The HD14 is a battery diode triode. The diode would be for signal detection and the triode would be the first audio amplifier in an AM broadcast receiver.
The Osram paper label. The pinch occupies a considerable part of the envelope.
The filament is a single oxide coated strand that passes vertically through both sections. The diode anode can be seen on the left of the right hand screen support.
The Type designation is etched into the glass within the typical M-OV elliptical outline.
The wide glass tube envelope is 29 mm in diameter and, excluding the B7 base pins, is 80 mm tall.
References: 1040 & 1043. Type HD14 was first introduced in 1940. See also1940 adverts.
