FWIW, the Golden Age ending with the beginning of the Silver Age was widely considered to be correct before there was a Bronze Age or a Copper Age. All the way up through to the end of the 80s, there were only GA, SA, and modern books. Since then, some differentiation has been made between Golden Age and Atomic Age.
I'm just saying that historically, many collectors and dealers consider Golden Age to include Atomic Age books. I personally would prefer them together because there are many runs of books that traverse both eras.