Instructions
Check the antique for any maker's marks. A good name can make all the difference to the value, plus the marks often change over time, helping to establish a date. Secondly, inspect the condition, making a note of even the smallest damage. Armed with this information, go to your local library and consult an appropriate price guide. Prefer a narrowly focused catalog, even if it is three or four years old, over a general guide because it is likely to be more accurate.
Read the appropriate entry with care. A guide will often give two or three price brackets for an item according to its condition with notes at the front explaining the criteria in more detail. Use this and your own jottings to establish a value for the antique.
Go to Google for a second opinion. Type the name of the item, your region, plus auction prices into the Google search engine on your computer. This should result in a list of recent or current auctions with a mixture of estimates and hammer prices. The estimate is an auction house's very broad sales guide, often less than a price guide value because it has to be pitched at a level to attract bidders. A hammer price is a final value at auction. Going through this process, you'll quickly develop a sense of how rare, or not, your antique seems to be. You may even be lucky enough to stumble upon its identical twin. There also are auction-collating services, which usually charge a subscription fee.