This 5Z3 is unusual in that it is branded Cossor but was made in America by RCA under the Lend Lease scheme in WWII.The 5Z3 is, in terms of general equipment, a high power rectifier capable of 100 Watts of output power. Such devices would provide the high tension (HT) rail for small radio transmitters, high power audio amplifiers, and modulators for amplitude modulation (AM) transmitters.
The Cossor paint identification on one side with the etched 5Z3 on the other.
The RCA Type identification lozenge. The anodes are folded and the stitches hold the metal tight to the support rods.
The RCA Logo.
The filaments are inverted 'v's of coated ribbon. The anode are 3 mm x 16 mm x 50 mm.
The top mica with the two filament tension springs connected to the central rods. These rods are held in place within the glass pinch but have no electrical connection.
This composite image shows the Lend Lease sticker that was added to the standard RCA carton. The wording shows the price of 18/3 and the fact that price maintenance was inforced by law.
The classic envelope is 50 mm in diameter and, excluding the UX4 base pins, is 119 mm tall.
References: Datasheet, 1040 & 1043. Type 5Z3 was first introduced in 1936.