This photocell is a mystery. The only identification is 405 and OR but this may not be the Type designation.
The construction is of a semi cylindrical photosensitive cathode and a ring anode in front.
The front view.
The top supports for both electrodes are fixed into a clear glass rod.
The thin glass tube envelope is 15 mm in diameter and, excluding the base pins, is 48 mm tall.
Updated September 14, 2020.