Much of what we know of as plastics were invented just prior to and during World War II in Germany. In the 1950's chemistry majors were required to take German in college because so much of the technical writing on plastics was only available in German.
There were no plastics in the 1920's. Containers for liquids made for human consumption were made of glass. Other things were in metal "tin" cans. There was no such thing as a plastic container. Piano keys and similar things made from plastic today were made from ivory.
Dolls for example had their faces, hands and feet made from ceramics.
Doing research was not this dudes strong suit. Buttons were often made of sea shells
I don't know why he mentioned the '20s...