Hi, I purchased this lamp at a garage sale last summer and it had a piece of tape on it that said Stiffel Lamp. I don't see any markings on this lamp that verify that it is a Stiffel. Do they have markings? I did a search of stiffel lamps and it does look like one. Also it appears to be pewter and it also looks like someone tried to clean it because there is some type of polish in the nooks and crannies. What should I use to clean it up better? Thank you!