Clever 1940s Blue Grey French 5cm Buckle

A clever colour, in some lights blue, in some grey and in yet others, almost violet.
A polished shiny lucite surface with subtle depths and variations in the colour.
And an equally clever design, straight lines and curves, all at the same time
5cm tall, and 4.5cm wide, gently curved for a perfect fit on your belt.
The inside aperture is just over 4cm tall and 1cm wide.
I found these in an old haberdashery warehouse -they are in excellent unused condition.