This vacuum photocell has no identification at all. The construction is of a semi-circular photo cathode with a wire frame anode in front but no blocking the light path. In use the anode would be held at a high DC potential through a large value resistor.
The electrodes side view.
The rear of the cathode.
The wide glass tube envelope is 25 mm in diameter, and excluding the B4 base pins is 88 mm tall.
Updated February 11, 2013.