Vintage Maxi Dress

Elegant vintage dress. My grandmother has a habit of cutting out the tags but she remembers purchasing this dress for a lunch date in Paris with the late Robert Haas (wine importer). Exquisite detailing on the top of the dress. The material is heavy, stretchy and almost sheer, but I am unsure of the exact type. I would guess a size Small as It fits me and I am xs- s.