The PE7B photocell from Mazda has Made in England etched into the glass as well as a paper label. The number 7434 is probably the serial number.
The underside of the composition base cap has the lettering BTH Co Ltd., it is possible, therefore, that this exhibit dates to the late 1920s when the Mazda brand was still made by BTH before the formation of AEI.
The PE7B shows typical photocell construction with a half cylinder cathode presenting a rectangular aperture to the incident radiation and a rod anode located at the centre of the cathode.
Side view of outside of the cathode. The lettering on the dome has the name Mazda in the centre with the words Photo-cell Type PE7B around the outer circle.
The wide glass tube envelope is 26 mm in diameter and, excluding the B4 base pins, is 87 mm tall.
Reference: Observation. Type PE7B was first introduced in 1929.