The STC CV2516 is also marked as the commercial 2C39A and is a planar design of disc seal construction. This UHF triode was designed for use in a co-axial cavity with forced air or water cooling.
The labelling of the valve is on the anodised aluminium cooling fins.
The very small gap between the long Copper anode and the grid mesh is clearly visible in the above picture.
The planar envelope is 32 mm in diameter and 66 mm tall.
