So, today's Girl Genius gives us a really good view of Bangladesh DuPree's neck and collarbones - I don't remember there being noticeable scars and stitching around the base of her neck before.

If you look at Act 2, Volume 2, Page 62, which is after the time-skip but before Paris, Bang doesn't have the scars and stitching around her neck.

They only appear after Bang fights the Geisterdamen in Paris. Did they cut off her head and did Gil need to sew it back on or something?