CV77, or "K tube"
This is described as a cold-cathode thyratron.
The device carries the serial number 4465, which is also written on the box.
The construction appears to be: a metal cylinder with a screw fastening, with a small wire running up within the body of the device. This can just be seen in the photo below. Within the glass section is a metal disc at the top, connected to the blue wire, and a metal ring below that connected to green at the side.
This file was last modified
10:40:21, Thursday April 14, 2022