This is a vanish from the Les Vernis Facettes collection, which must be an older one, since it has been discontinued for a long time. All shades of Les Vernis Facettes are iridescent if not even duochrome; Clair-Obscur shifts between lilac and yellow/gold (although the yellow part is quite hidden). Notice the mattified appearance of the outer square cap as well as of the bottle.
Three coats; Clair-Obscur also has a pearl finish. It’s a lovely shade and quite extraordinary.