Atomic age,but that really didn't make a whole lot of common sense,since the Atomic age began in 1945
Usually books pre-1935 are considered Atomic-age
Then again when I was into books everything was Golden,Silver and modern
Modern was 20 cent covers to current at the time (1992)
the true silver-age was the idea of 15 cent covers to most people back then,hence 20 cent books being modern
Now Bronze and copper is just silly to me since it should POSSIBLY be Bronze, Feces and then Modern due to what was released from 1985-1995
It is silly TBH,following a metal chart.
We used the term Golden-Age much like our parents did to describe when they lived,the golden age of life in America.
Silver was coined from the age of the super-hero
Atomic Age books were those books our grandparents knew and we would never see outside of a museum or massive comic show and we had little to no interest in them at that time
The rest is just a need to categorize everything IMO