Sophisticated, tiered collar dress, most likely from the late 30s or early 40s. You know us with our fabric knowledge...but my best guess is a soft, raw silk. Has back zipper. Some light discoloring on the white collar and near the pits. Seems a little unfinished, as seen in last two photos, and could use a little stitch at the seam on the cuff. Otherwise, in pretty great condition! Would work best for an XS/S, but please refer to measurements below. (Modeled on a size small with a 6 month preggo belly).
With garment lying flat and relaxed, measurements are: