During an idle Google search the other day, I found a link to this web article, in Russian, about the Pskov finds. There were several, but the others did not have textile remains.
I ran the article through Google Translate to get an English version that I could read. Judging by Google Translate's translation, the grave that contained the large fragment believed to be a shift and apron dress was robbed in antiquity--probably between the 13th through 15th centuries. There were other metal items found besides the tortoise brooches, including "chased binding, broken bead of silver wire, round silver pendant ornamented with a triangle of grain, ring-shaped fibula with a needle and scraps chain". The article mentioned the textiles wrapped around the tortoise brooches, and supplied this description of the figured silk trimming: "In the process of restoration of tissue revealed that it consisted of strips of silk, on which the medallions are depicted with the fantastic animals and flowers."
I commend the article to your attention, whether or not you read Russian. It includes good color photographs of metal jewelry and other metal artifacts from all the Pskov sites, including some highly ornate tortoise brooches.