The Retro Era lasted from 1935-1955
In the 1940s, there was a shortage of precious metals due to their use in World War II. Restrictions were placed on the use of precious metals, especially in luxury items such as jewelry. In turn, jewelers were forced to use their creativity, making more hollow, lightweight pieces using as little gold as possible.
Rose gold, white gold, green gold, and other combinations of low karat gold gained popularity during the Retro jewelry period.
Due to the shortage of precious metals during the Retro Era, it wasn't uncommon to recycle old jewelry when making a new piece.