Based purely on the number of pieces I am currently seeing here, on virtually every vide-grenier and brocante, I'm inclined to go with Ivo and KevH, and stylistically this is right for French. Opaline, and anytime from mid 1800s onwards. I am also regularly seeing comparatively modern opaline vases, in old patterns, still bearing paper tags("fait a la main en Lorraine") for glass factories in the Alsace-Lorraine region.
regards,
Le Casson