I received a partial Roger/Berry Coronet button card today that points to an answer to a mystery.
These are Beauclaire style buttons!
Roger Berry was a wholesaler/distributor rather than manufacturer. I have never found a reference as to who made Coronet buttons. The new card suggests that General Plastics made the Coronet brand buttons, and used Roger Berry as a wholesaler or distributor. General Plastics only started to use the brand name ‘Beauclaire’ from around 1951. The Coronet cards look older: I suggest that Coronet was a brand name used in the 1940s.