Original casein (plastic) button from the 1940s-50s.
Square shape has mitred corners, and a round button feature drilled on the face of what we call "grey dark chocolate" colour (actual colour differs slightly from image shown).
 
This quality vintage button is "as new" condition.
Height of button calls for a larger buttonhole on woven fabrics.
 
25mm diameter (19mm x 19mm), 7mm high (base to top edge); 4 hole sew through.