The factory mark on an antique vase can give a clue the age and the value of a piece. The mark can tell you if a vase is a Wedgwood or a Weller or if it is Japanese, Italian, English or American. The factory mark may let you know when the vase was made.
Identify the material of the vase. Most pottery and porcelain will have a maker's mark, either stamped under the glaze or inscribed in the porcelain. Silver will have a hallmark, indicating the factory and date, and will be marked sterling (or simply "925") or some variation ending in "plate." Glass or crystal sometimes has a faint, etched signature, which can add about 25 percent to its value, according to antique experts Ralph and Terry Kovel.
Find the factory mark. For most pieces, it is usually on the bottom, although sometimes glass or crystal will have a faint, etched signature that could be found on the stem near the base or at the top. Other pieces may have no mark at all because their factory mark was a sticker or paper label. These tend to be more recent pieces. Some marks can be quite small; you may need a magnifying glass or small flashlight or penlight to clearly see the mark.
Look for factory names, hand-painted signatures, name of country or origin or other images. Sometimes a mark will clearly indicate the name of the maker; other times it will simply be a set of initials, numbers or picture of an object or animal. In addition to the factory mark, there may also be what seems to be a hand-written name. This may be the artist who hand-decorated a piece. Pottery painting was a popular hobby for ladies in the early 20th century, and many signed their pieces. This hobby has seen several resurgences, so a signature alone is not an accurate indicator of age.
Use a dictionary of marks as a tool to identify the maker of a piece. These guides will usually have a clear picture of the mark and list the factory name alphabetically. They also help identify the age of a piece by giving the dates a factory operated. Price guides are usually company-specific, but they may also be helpful in narrowing the age if the name of the company is clearly stated.