That particular cloak was sold off the shelf at Duskruin as 6/140 (normal Max L/D), which corresponds to a "Huge" inspect. Special Duskruin deepening would have taken it to 160 (Incredible), 180 (Enormous) or 200 (Gigantic).
That particular cloak was taken off the shelves a couple Duskruins ago, but whisper cloaks in general were still available last Duskruin.