It looks like a soft burgundy velvet, possibly satin for a substitute but I love this velvet. Typically velvet is not a good choice, if it is crushed velvet it isn't period but true velvet is too stiff. This velvet looks like a true velvet that doesn't have that stiff back. The front panel looks like a satin, not a brocade but it could be substituted... Plus the beautiful gold satin sleeves! Luckily, the pattern for this has already been purchased. Twice, actually.
I'm not sure if I want to use the Simplicity pattern or the Period Patterns pattern. I find that the Period Patterns come with very vague instructions and too much 'refer to...' type setup, but they are the more accurate period patterns and the lack of real shape in the pattern makes it easy to alter (with a few muslin mock-ups). Alternatively, the Simplicity pattern is easier to use, fairly easy to alter for the right fit and has directions that are miles better than the vague instruction pamphlets that come with the first. I suppose I could make mock-ups from muslin of both patterns, see which fits better in full garb, but I do hate to buy fabric that will simply be thrown away. The other downside to Period Patterns is the way that patterns are printed, with multiple styles on the same pattern piece. Basically, this issue is worst in the bodices; when you cut into one bodice for one style you are cutting another bodice apart. So that leaves you with two choices; buy the pattern because you like it for one specific dress, or trace each piece on butcher paper so that the original pattern isn't being cut. We shall see, that project is a long time in coming, so it will be a bit before you see another post on this dress.