The AC/P is usually seen as the later construction as typified by the AC/P but after the merger between British Thomson-Houston (BTH) and Metropolitan-Vickers (Metrovick) the first AC/P was this shortpath version - probably made at the Metrovick works.
The classic shortpath construction with the grid held by a single support and looping back into the anode.
The brand and Type designation is etched into the dome of the envelope.
The top supports and the anode 'wings' for cooling.
The heater and cathode are placed closer to the back of the anode channel. The grid support appears white.
The back of the anode showing the main anode support.
The balloon envelope is 55 mm in diameter, and excluding the B5 base pins is 109 mm tall.
References: Data-sheet, 1040 & 1043. Type AC/P was first introduced in 1929.