If you want more information on old lamps to help identify your own, you can first consult a book. However many such books that I've seen feature American products. But this would only be for your information. If you seek to validate your lamp and want a written appraisal, you need to get in touch with a certified appraiser. Check out the American Society of Appraisers, or the Appraiser's Association of America for a professional in your area.
Make sure that the appraiser has experience with old lamps. Find out how much the service will cost. Appraisal costs vary depending on where you live, and how much time the appraisal will take. The service is not cheap.
Do as much research as you can on your particular lamp. You don't want to spend more money on an appraisal than the lamp is worth.