An Art Deco period French opalescent glass dish. It is of quite thick construction and has a bubble type design. There are no makers marks, but from the design and colour I suspect it is either Ezan or Sevres. At the size it was likely intended as a bonbon dish or similar. It has a strong blue opalescence as can be seen in the images.
A couple of tiny nibbles around the inside rim. Some wear to the base.
Height: 2.7 cm ( 1 1/8 inch )