Ever wonder what the model number of your Zenith really means? According to the original factory service manuals, there was a coding system they used. Say your radio is a R500WH model. Here is how it works.
R = Zenith Royal
500 = Family
W = Color (white)
H = Model
Here are the color codes Zenith used with their transistors:
F=turquoise or two tone green,
G = grey
J=two tone brown
L=tan or beige
Y=black or ebony
The model number codes were printed on stickers and put on the stock boxes for identification like this Black Royal 500 model H.
They also sometimes put a sticker on the outside of the radio on the bottom like this Beige Royal 475.
With many models, they put the sticker inside on the back half like this yellow Royal 50 Model L.
But there are also models that I have never seen a sticker on like Royal 60, 90, 100, 125, 150, 200, 300 & ealry 500s.
The stickers also have the serial # of that particular radio. I feel it is a plus to have a radio that still has this sticker in readable condition because many radios are missing it.
As you can see, Zenith was not real consistant where they put these stickers. Here is where I have found them:
Inside the back cover: Royal 20, 40, 50, 50H/K & L, 59, 80, 85, 130, 185
On the outside of the radio on the bottom: 400, 475, 500L, 500N
I believe that all the cartons had a serial # sticker on them and in 1961 Zenith started putting a matching # sticker on the radio, but this is hard to verify because cartons are so hard to find. I have had Royal 500B cartons with stickers, but no sticker was on the radio. This leads me to believe that Zenith did not start putting stickers on the radios until 1961.
Hope this helps you. Now go look for those stickers!