THe sgain dubh (black knife) is a short knife traditionally carried in the top of one's hose when wearing a kilt. It evolved, I believe, from a blade called the sgain achles (sp?) that had a longer blade and was usually carried hidden in the armpit. When the Hanoverians outlawed the Highlanders from carrying any blade over a certain length, deeming them to be weapons, the Highlanders evolved the sgain achles into the short-bladed sgain dubh. The name, "black knife" comes from the fact that the hilts were usually carved out of an extremely hard and dark wood, frequently in a Celtic interlace pattern. As the wearing of highland dress became less and less of a day-to-day item, the sgain dubh became more and more a piece of male jewelry and that is when you begin to see them with cairngorm stones set into fancy silver mounts at the pommel and with all sorts of other silver trim on them. A similar misfortune befell the Highlander's dirk, a once fearsom weapon that became a form of male jewelry during the Victorian era.
I have seen some very nice sgain dubhs that were made by such custom smiths as Al Massey up in Nova Scotia. The Hanwei version by Paul Chen that SAC Iberia sells is more of the "male jewelry" mode than of the working knife mode, despite its "Damascus"* blade. I am certain that you can find better for the money.
* Better called "pattern-welded".
