Finding An Appraiser
If you suspect your item is worth a significant amount, then a professional appraisal will be your best bet, as it is more difficult to research pricy items online. Someone really needs to be able to see and touch your item to make sure it is the real thing.
You should be able to find a local appraiser in your yellow pages. Otherwise, you can go to the International Association of Appraisers website and do a search for a licensed appraiser in your area.
Many times, your local antiques dealer may be a licensed appraiser or they can point you in the direction of an appraiser that they know.