The CMG7 is clearly a photocell and the screw top caps indicate that it was made in the early to mid 1930s. It has a B4 base cap that has the M-OV identification moulded into the underside. No operating details have yet been located.
The light admitting window and the two screw cap connections. There are also two evacuation pips.
This exhibit was kindly donated by Murasaki Neko in 2021.
The wide glass tube envelope is 34 mm in diameter and, excluding the B4 base pins, is 142 mm tall.
Updated October 29, 2021.