The DAF96 is a miniature dry battery valve exhibits very low filament consumption. This is one of a later generation of dry battery valves from Mullard in 1953/4. It was designed for detector and first audio stage use in battery portable domestic radio receivers.
The thin glass tube envelope is 17 mm in diameter and, excluding the B7G base pins, is 45 mm tall.
References: Datasheet, 3002 & 1040. Type DAF96 was first introduced in 1953.