The U14 was intended to meet all HT requirements up to a maximum of 120 mA at 500V, using a capacitor-input filter. This exhibit has solid sheet anodes and no branding and is thus a generic implementation of the M-OV design.
The sheet anodes are stitched together. The ribbon filament can be seen welded to the supports above the pinch.
Here it can be seen that each filament ribbon is oxide coated and the oxide is white. The lower ends connect directly to the supports from the pinch and are not held by a bottom mica sheet. The tops are held by a mica sheet that touched the top of the shouldered envelope.
The classic envelope is 45 mm in diameter and, excluding the B4 base pins, is 100 mm tall.
Reference: Datasheet. Type U14 was first introduced in 1931.