The Sears DIY book is from 1969 and cost 50 cents originally.
I don't know what the original price of the 1931 NEC was but, I paid $16 for it at the used book store. (Alan Nadon)
These three Codes are all older than I am.
The one with the black cover was a hand out co-sponsored by Cutler Hammer, Square D, Trumbell and Westinghouse. In 1937 even electricians were hard pressed to be able to buy a Code book. They included insert pages of diagrams and references to their products to justify the expense.
I think a little "artistic license" must have been employed there!
They should revoke that license. Problem is is that some DIYers will take it literally, that it would be okay to uild it that way.
I've had to argue with marketing and sales types about advertising copy and such on products I had designed. "But it's just some artwork.", "The customers will takke it literally, I would know, I'm like the customers and I'd do that...".
I remember when Sears sold entire service "packages" that included SE cable, clamps, panel, breakers, everything. They went away before I was old enough to buy any them, but I do remember them in their catalog in the 1960's and 1970's.