Greentown Glassware is highly collectible and valuable glassware often sold on eBay. Please be aware there are reproductions of some of the Greentown pieces. There is also some confusion about what pieces are attributed to Greentown vs. other glass makers. There can also be many claims of a glassware item being Greentown glassware, when it is not. Most sellers will correct their listing, when they learn their piece is not a Greentown item. Some though, do not change their listing and list their pieces with false information, which makes the seller seem knowledgable and their pieces authentic, when they are not. Not all chocolate colored items are Greentown, as some believe, and the glassware was seldom offered in white and not offered in blue slag, vaseline or custard colors....information to provide potential buyers with a start of information. The molds are also not mismatched and pieces are well-formed. Ask sellers to list their sources for authenticating their pieces and then check the photos in these sources carefully. I've had a seller insist he was selling Greentown glassware, citing the resource book, but his piece and the photo did not match. Further investigation and checking saves money! The National Greentown Glass Association and the Greentown Glass Museum both sell books to assist with identifying authentic Greentown pieces and to help identify reproductions, which exist for some patterns and colors. Books edited by Meassel are the most current and thorough and build from Dr. Ruth Herrick's original book, which is now outdated. Use these resources when purchasing Greentown Glassware, especially when the piece is more expensive. Be aware there are currently pieces being sold, which are claimed to be Greentown, when they are not and the seller will not change the listing.