Glass Lampshade for Ceiling Light

This lampshade was bought in France and shades of this general shape were very popular there over a long period. That said I can't be definite about the period.

This example is more ornate and well executed than the many other examples I've seen in my years of searching French car boot sales.

Image one....the top surface of the central part has a gritty texture (frit).

Image two....the underneath surface is glossy with a coin dot pattern ( concentric circles of bumps).

Image three....the outer section is vaseline glass which can look blue or white. The shell like shape reminds me of The Sidney Opera House.

Image four....here I'm trying to show the delicate lime green and pink spatter found in the central area.

I just wonder whether anyone has seen this shade and may know something about it.