The Mantle of Tegau Eurfron and Eluned's Stone and Ring are treasures number 14 and 15; however, they do not appear on every list and when they do, Rhygenydd's crock and dish are made into one treasure and one of the other treasures are dropped so that the number stays at 13. Neither one of these are traditional, but as they do appear, I thought that they should be recognized. Sort of like recognizing Never Say Never Again as a Bond movie, when it really isn't.
Tegau Eurfron's Mantle belonged to Eurfron the Fair (that's what the Tegau part stands for). She had a nickname - gold breasted (wow, all sorts of James Bond references this post). She got bit by a snake on her breasts and they had to be removed, so she had gold ones built to replace them. This story does not survive in the English versions, but there is a French romance that includes it. This mantle is much like the other treasures: only a woman who has been chaste could wear this and have it fit. Women of the more, er, experienced type, would find the mantle too short (which probably suited their purposes anyway).