Maker's Name: 
16.5 × 16.5 × 48.5 cm

This is a jacket in which the thimble of a water-cooled valve was inserted. Distilled water was circulated by a pump from a large tank of water at a higher level than the jacket. The water was regularly tested for conductivity and replaced when the water was no longer a good insulator. It was of course at the same potential as the thimble/anode of the valve, in the region of 12kV.