The value of any antique can be determined by an appraiser. When having any item appraised, it is best to go to someone who is accredited and meets professional and ethical standards.
It is possible to check the credentials of an appraiser through the American Society of Appraisers, the Appraisers Association of America or the International Society of Appraisers. Each organization has its own website that can be searched to find appraisers in specific locations and with specific areas of expertise. Most appraisers charge a fee for a full appraisal that documents a full description of the item, the process used to determine the item's value, and the estimated value of that item.