When identifying an antique lamp, consumers may need to determine the history, age and period of the lamp to assess its historical relevance. This can be done by examining the lighting fixture for casting or foundry marks, which are believed to have been used by the installer to identify the parts and avoid duplication. Casting marks are often numbers and symbols and help distinguish originals from reproductions.
Examine the base of the lamp. Tiffany Studios, a renowned maker of lamps during the early 1900s, always made lamps with a bronze base. An antique bronze base would reveal a golden brass color if scraped using a fingernail or a metal screwdriver. If it shows a reddish gleam, it is most likely copper. Most manufacturers also place nameplates, stamps or a sticker at the bottom of the lamp.
The condition of the cord and plug also reveals if the lamp was manufactured during the first half of the 1900s. Check if the cord is covered in cloth or cotton and if the plug is open at the end with the screws showing. This should indicate that the wires and the plug are old. If the wiring looks new, the previous owner could have replaced it.
Check the head and the glass of the lamp. Knock it lightly; age and the drying of the wax used to hold the glass together should falter a bit and the shade should rattle a little. It is important to check both the base and shade of the lamp and not to assume that they came as a pair.