This gown is based on a picture and a pattern draft in Norris - Medieval costume and fashion. I'd say it's rather not period but I had to give this a try. I quite love the finished gown, though it's rather heavy. But I managed to get the back neckline properly while still having enough support in the front for a rather large bust without resorting to any supporting undergarment.
The fabric is silver silk with hand embroidery and a lila tussah silk (it's raw silk that's woven similar to wool).