Here is a list of manufacturers that mark or sign their glassware, some of the makers will almost always mark their glassware, while others will only mark certain patterms or lines-some unmarked product in that company could signify a second quality piece.
Baccarat-Cartier-Christian Dior-Daum-Edinburgh-Faberge-Hawkes-Laliwue-Ralph Lauren-Lenox-Lorraine-Moser-Orrefors-Peil-Spode-St. Louis-Steuben-Staurt-Tipperary-Tudor-Tyrone-Val St. Lambert-Waterford-Webb Corbett-Thomas Webb.
Manufacturer's that sign product other than their own name listed below:
Josair( crown symbol)-Lenox ( "L" in wreath or a broken circle in Logo)-Oneida ( intertwined OC)-Rosenthal (script R)-Orrefors (of)-Royal Doulton (crown)-Schott-Zweisel (Z in block)-Spiegelau (S)- St. Lambert (VSL)- Webb Corbett (Crown)- Thomas Webb ( Webb)
To locate hard to find patterns look up Replacements, Ltd out of North Carolina.