Courtesy of the Met, of course.
And here's where things are at the moment:
Consider the irony of the "recycle" emblem on the box. Thank you.
The retro-looking brown stuff is to be the lining. I am using it as the lining because it's convenient and free, and because it bears more than a passing resemblance to some of the astonishingly modern-looking cotton prints from the London Foundling Hospital billet books.
A textile from one of the London Foundling Hospital billet books, entry 6671. From Exhibiting Fashion.
The authenticity of the print doesn't worry me much because the fiber content of the exterior fabric is far more uncertain. (Impeccable reasoning! I haz it!) The gold brocade contains nothing truly synthetic, as best as I can tell, but it is probably a cotton/silk or rayon/cotton blend. Furthermore, I'm not sure if a fabric so heavy would have been used for a dress. (For those of you playing the drinking game at home, this dress was actually started BEFORE this happened.)
With that encouraging denouncement of my costuming integrity, onward and upward we go!