Kanawha Glass Company
My wife learned the hard way that labels (or stickers) add value to art glass. As a child it always bugged her when her mother left the labels on things. She thought it detracted from the looks of the glass. So when we set up housekeeping many years ago, she took all the labels off.
Fast forward 30 years and now she is buying art glass on Ebay. Since much of it looks the same and/or has been reproduced, the label is suddenly important and she will pay more for art glass with the label intact.
For a quick education about the value of labels look at the Ebay auctions listed below. They all include labels and if you look for identical items without the label you will quuickly see a difference.