I would take it to either an antique store or a lighting store and see what they know. I had a friend that bought a lamp at a barn sale for $4 and it needed a shade. She took it to a professional lamp shade store (yes, they have them!) and she found out it was an antique lamp worth over $400! I don't think she would have gotten this information if she didn't go to the specialty store.
Love the lamp by the way, I am so into vintage and kitschy!!!