Bomac 1B27 TR Cell for use in an external cavity. Also CV713. The frequency range is 2.3 to 3.8GHz and it will handle 450kW.

The tube measures 82x26mm overall (across the disc seals), 16mm between the disc seals, and approx 20mm across the glass.

Markings on the device are JAN-CBNQ-1B27, and the numbers 160 and 140.

The keepalive connector has a cutout to make space for the exhaust seal. At the other end is the tuning screw.

The gap is shown here. In this picture the tuning screw acts on the left hand side.