These are 17mm (about 5/8") from corner to corner and 13mm (about 1/2") from edge to edge. These are an early plastic, possibly celluloid. Some have discoloration, and they will need to be cleaned. They are almost 90 years old, made during the great depression with an art deco aesthetic.
345 pieces vintage early plastic art deco depression era green square diamond 2 hole buttons destash bulk lot.