The 3Q4 miniature dry battery output pentode was designed for radio receiver use. The output of 0.27 Watt maximum would only drive a small efficient loudspeaker, not hi-fi but quite loud in a small room.
The preference for British made products in the post-war period, to save spending foreign currency on imports, is typified by the pejorative labeling of Foreign for the country of origin.
The reverse of the envelope.
The spot welded seam on the bright anode.
The base pins clearly showing the multi segment construction to offer a strong pin on the outside and a wire with an expansion co-efficient to match the hard glass base disc passing through the glass followed by more wire within.
The thin glass tube envelope is 18 mm in diameter and, excluding the B7G base pins, is 45 mm tall.
References: Datasheet, 3002 & 1040. Type 3Q4 was first introduced in 1950.