Examine the base of the vase for a very small, pea-size design. This is the most common location for a Waterford mark. The Waterford stamp is the text "Waterford" in a serif type font, almost medieval in its appearance, with a detailed capital W. The individual letters of Waterford have noticeable gaps within their design.
Run a finger over the base to feel for any indentations that might reveal a faint or hard-to-distinguish mark. Examine the area with a magnifying glass to better reveal a mark.
Check other unobtrusive places on the vase such as the underside of a rim or turned-down flap. Waterford crystal makers do not like their mark to detract from the piece itself, sometimes making the mark hard to find.
Take the vase to an antiques expert if you have difficulty locating the mark. It is extremely rare for genuine Waterford crystal to contain no mark at all, but an expert will be able to identify the vase by its patterns alone if necessary.