1957 Zenith Royal 500, second version — 7ZT40 chassis series
Coat pocket radio, nylon cabinet
5 3/4 x 3 1/2 x 1 1/2 inches / 146 x 89 x 38 mm
Seven transistors (Zenith ovals, 2N15, 3x 2N35, 2N93, 2N194, 2N216)
Superheterodyne circuit, vernier tuning
Four 1.5-volt AA cells
Manufactured by Zenith Radio Corp.; Chicago, Illinois
The second version of the Zenith Royal 500 — 7ZT40 chassis series: vernier tuning and a printed circuit board were the big changes here.
All these versions shared a nylon cabinet, a material not used all that often for transistor radio cabinets -- the vast majority of transistor radio cabinets were made of ABS, a version of polystyrene that was much less brittle than plain polystyrene but still far more susceptible to cracks, chips and scratches than was nylon. Zenith's "UNBREAKABLE NYLON" stamp found on the back face of all 500 cabinets clearly was a claim that went too far: some small percentage of cabinets today can be found cracked or chipped -- yet to this day, many nylon radio cabinets are not only free of damage but have retained that wonderfully glossy "like new" finish that few ABS cabinets have managed to hold onto without restoration.