At the turn of the century, many French companies were making cameo glass, which is made from layers of different-colored glass. An artist etched away parts of the top layers to form a color picture with the remaining glass.
Prices of antiques are determined by their rarity, quality and availability. The signature of the company or artist is a plus that almost always adds to the price.
Cameo-glass pieces made by Galle, Legras, Daum, D'Argental, DeVez, Degue and others appear to be similar to the novice. Fortunately most of the pieces are signed with the maker's name.
Look on the sides of a cameo-glass vase for a signature that seems to be part of the design. Often the names are written vertically in oddly shaped letters.
Unfortunately, since the 1970s there have been copies of cameo glass that are signed with similar names. Instead of the name "Galle," for example, some new glass is marked "Galli." When an auctioneer reads the name to a crowd it sounds as though the vase were made by the famous artist, not a new company.
There are ways to sandblast a mark on an old piece so the mark is raised and appears to be original.
If you have a family heirloom cameo vase with a signature, it is valuable.