Written vertically in green ink on the glass envelope.
Printed in tiny black ink toward the bottom of the metal base.
overall: 8 3/8 in x 2 1/4 in x 2 1/4 in
This object is a mercury half-wave rectifier within a glass envelope with a large-metal-shell super-jumbo four-pin bayonet base and a cap for the plate at the opposite end. The circumference of the base is metal, with a ceramic bottom through which the pins project. There is a small protrusion on the side of the base positioned between pins 2 and 3. At a mercury vapor temperature of 20 to 60 degrees C, the tube is rated at 5000 V forward voltage at 5 A maximum peak current. A circle made with yellow ink surrounds the cap at the top of the tube.