So there's an archaeological find that's recently been made public of some amazingly preserved 17th century textiles found in a shipwreck off the coast of the Dutch island of Texel. (http://www.thehistoryblog.com/archives/41653
There is a nicely huge photo of a complete pair of silk stockings in there, and I've been staring at the heel flap and gusset construction, because something about the sole looked unusual. (Huge photo linked from the above article. Zoom in for more detail: http://www.thehistoryblog.com/wp-content/uploads/2016/04/Knee-socks.jpg
The gusset begins much sooner than I'm used to - it looks as if it starts above the ankle bones?
The heel flap (green in my sketch) looks like something I've seen in a Nancy Bush sock book at the library: a dart gets decreased away at the end of the flap, and then the whole thing is folded and the end is seamed to make a pocket, instead of turning the heel. Then stitches are picked up along the edge of the gusset and the sock proceeds as usual. (I'm going to try to get the book out of the library again.)
This was a little odd, though, and it took me a while to figure it out: there are increase stitches making a triangular gusset on the bottom of the sole. I've sketched the sole: the green is the seamed-together heel flap, and the tan is the new section of increase stitches, which replace a bunch of stitches that get eaten up by the really long lines of gusset decreases.
What do you all think?