Determining the value of an antique vanity involves determining if it's actually old before searching for hallmarks that mean the piece is valuable. Guides such as "Antique Trader Furniture Price Guide" and "Millers Antiques Handbook and Price Guide" can further help nail down the exact value of an antique vanity.
To determine if the vanity is actually old, much less an antique, run your fingers over all the edges. Sharp edges indicate a new construction, no matter how old the piece looks. Look more carefully at the sawn edges for a curved pattern. These are left by circular saws, thus indicating the piece is newer.
Check the screws. An off-center slot indicates the screw is probably old. Likewise, the veneer probably has an uneven coating. Finally, check the mirror glass. If it's thin, variably wavy and grayish, it's old glass. If the mirror has been replaced, this devalues the piece even if the rest is antique.
To further help determine the value, look for fine, vigorous carving in the Chippendale style, which increases the value. Likewise, more ornate designs increase the value.
To know the exact value of an antique vanity before purchase, consult a pricing guide or consult an antique website. For example, Kovels.com offers a free price guide for antiques. The more information you have for the searchable site, the more accurate your value quote.