Vintage Amethyst Glass Intaglio Portrait of Frederick the Great

This is an unusual Vintage Amethyst Glass Intaglio Portrait of Frederick the Great, who ruled the kingdom of Prussia from 1740 to 1786.  The classic portrait shows a three-quarter view of his unsmiling face, turned toward the left.  His hair has widow's peak and two rows of curls.  Below him, his abbreviated name is carved in German, "FRIEDR. DER GROSSE." This portrait has been reverse carved into an oval piece of amethyst glass, measuring 1.4375" (37mm) high by 1.1875" (30mm) wide by 0.125" (3mm) thick.  The front has a curved surface which is beveled to a flat back..  There is a 0.0625" (2mm) at the top.  Maker and exact age are unknown, but this portrait looks very similar to ones made in the 1940's in Czechoslovakia.  This Vintage Amethyst Glass Intaglio Portrait of Frederick the Great is in very good condition.  There is several tiny chips along the back edge which can be easily polished out.