This is valuable information to me. It's wonderful to see the work of less celebrated clothiers.
I have an extant gown, dressmaker made, from ~1882 that uses a similar type of flat piping that Celestia used. It was far more elaborate though, 3 layers of bias tape (blue, beige, blue) basted together and backed with horsehair. Basted against the raw edge of the dress fabric. No finished edges anywhere! Just because it was dressmaker made doesn't mean it was fully finished!