I was pleased to receive these buttons from my friend Olwyn. She bought them in an Antique Shop in Sharlottetown, Prince Edward Island in 2014. (That is the place of Anne of Green Gables fame)
They are quite different being square and two coloured, having a design pressed into the thin sheet of Celluloid. The shank is of Celluloid also and they are a little under 3 cm .