The Retro Era lasted through World War II and featured unique jewelry designs unlike any other era before it.
During the 1940s, there were restrictions placed on precious metals due to their use in World War II. In turn, jewelers were forced to use their creativity, making more lightweight, hollow pieces using as little gold as possible. It wasn't uncommon for customers to recycle their old jewelry when creating a new piece.
Rose gold, white gold, green gold, and other combinations of low karat gold gained popularity during the Retro jewelry period (circa 1935-1955).