According to the U.S. Customs Bureau, an item is considered antique when it is over 100 years old. Collectible items don't have to be old, but must be rare or wanted by collectors. Some humble looking objects can be worth thousands of dollars, if in good condition. Determining the value of an antique or collectible is best done by a professional appraiser, but you can still find an estimate of an object's worth with the right tools.
Examine the object for identifying marks. Manufacturer's stamps, dates, and artisan signatures can all make the process of appraising an antique or collectible much easier, say the experts at the Pratt Library.
Note any patterns, decorations, or particular styles. These can be used to determine the era the piece was produced in. In the case of china or silverware, the pattern is often the only way to identify it's identity.
Use antique price guides to find a rough estimate. These guides are updated each year, and reflect the actual auction prices of thousands of antiques and collectible items. Many of them also give quotes for collectible items that are not considered antique, say the experts of the Kovels' Antiques and Collectibles Guide.
Bring the item to a professional antiques and collectibles appraiser. If the item is too large to move easily, take a variety of clear digital photos, especially of any maker's marks or manufacturer's stamps.
Search online auction websites and antique or collectible dealer's websites. Once you've identified your item, research what price others are listing it for. According to My Granny's Attic, searching through sold items and finished auctions can give you the most realistic estimate.
Attend an appraisal event. Some antique and collectible items dealers will hold events where they invite members of the public to bring in items they wish to have appraised. This can be much less expensive than having your items privately appraised.
A private appraisal can be expensive, so doing some basic research on the item to determine it's age and possible worth is recommended.
Even if you're not interested in selling the item, it can be good to know the worth of an antique or collectible so you can take proper care of it. For example, an antique side table can lose all of it's value if refinished.
Do not attempt to clean or scrub a dirty item if you suspect it is an antique or collectible. You may destroy important marks or ruin the item's original finish.
Do not contact an antiques or collectible items dealer without a professional appraisal. They will not be interested in your item unless you have proof of it's worth.