IS THE GLASS ITEM MARKED?
This is one of the questions that most sellers of glassware are familiar with. We get asked several times each day about several different pieces, even if the information is in the listing and even if it is shown in the listing. That issue aside, the question itself is somewhat troubling. The reason it is asked is because often times, beginning collectors see the mark as a sign of assurance that the piece is authentic. Nothing could be less true. Following is some information on various makers of glassware and their marks that will help to show why this is such a dangerous or at minimum, insufficient means of testing glassware. Labels are even worse as they can be moved from item to item by unscrupulous sellers and even if not done by the seller, the seller may have been duped when they bought the item with the label.
Lets look at NORTHWOOD GLASS. Many of the early pieces were not marked. Many were. Sometimes even on identical pieces, one would be marked and the next not. An example would be the Tree Trunk Vase. If you look around ebay, you will see several of them most of the time. There are typically examples of those that are marked and not marked listed at the same time. Is the marked one more valuable? Only to those who do not know better. This pattern has never been reproduced and is clearly identifiable in all the Carnival Glass Books and online sites dedicated to the collecting of carnival glass. It is also shown in many Northwood Glass books. Northwood glass marks are also muddied by the fact that L G Wright made a mark on some reproduced items which looks nearly identical to the original mark, but has the line beneath the N slant down to the circle. This one confuses most newer collectors.
HEISY Glass is the same way. LOTS AND LOTS of Heisey is not marked. It does not make it less valuable. It does not make it fake. It makes it great glass that just wasn't marked when it was made. The H in a diamond question has been asked of almost anyone who has ever listed Heisey. Yes, it is an easy way to see the makers mark and HELP identify the maker as Heisey, however, there are pieces marked with the identical mark that are FAKES, such as the blue hen on a nest that is marked with the H in a diamond mark of Heisey. Heisey did not make it. They did not commission it. It is an outright fake. Yet it shows up at antique stores, shows and online, including ebay as Heisey and typically sells high because so many inexperienced buyers think the mark makes it authentic.
Most Depression glass is not marked with the makers mark. FEDERAL marked some of theirs with an F in a shield. ANCHOR HOCKING marked some with an Anchor. And Hazel Atlas marked some with an H with an A beneath / within it. But most of what is now considered to be Depression Glass is not marked.
Art Glass is the same. Blenko marked their glass in 1958 till 1961. They then stopped marking their glass with a permanent mark until 2001 when they experimented with an impressed mark which included the date. They have marked many items since with a Sandblasted mark which includes the name.
Fenton Art Glass started marking their items in 1973. We often get emails from people asking for old Fenton from the 1920s and 30s that are marked with the Fenton logo. When I explain to them that they did not mark them at that time, inevitibly one of two things happen. Either they email back to explain that I am wrong, or they email to tell me about the great piece they bought for an outrageous price that the seller assured them was that old. All of this information can be confirmed for free online. Just search Fenton Marks. You can also find information on the artist marks used on their baskets, and so much more information is right there waiting for you to look at it.
Imperial Glass is similar to Fenton in that they did not mark their glassware until 1951. Older Imperial Glass is not marked.
The examples are endless of the unmarked glassware to be found on ebay and elsewhere. Research is the key. That and finding a seller with a very good reputation who has been around for years and will stand behind their items. We suggest buying from us of course, but you can find other good sellers on ebay too. Just know what you are buying and throw away the "is it marked" question as it is not a great means of determining if an item is authentic at all.
Good luck,
We are always available to answer questions.

)