Vintage Brief Originals blue floral silk(?) 1960s wiggle dress

Absolutely gorgeous blue, black and white wiggle dress in what I think is a lovely silk? The tag has enough wear that it's no longer readable (see photos) but it's so soft and the shell doesn't feel remotely synthetic. The lining seems to be a poly of some kind. There's fraying here and there, especially inside the dress, and there's visible wear along the collar and shoulders, but it's really only visible if you're looking for it. Two external belt loops on the sides and one pass-through hidden loop on the front. See photos for measurements.