Many collectors of incandescent lamps restrict their interest to lamps that were manufactured before a certain year. For example, one might choose the year 1925, when the inside frosted lamp appeared. Identifying and dating lamps can be confusing because of the several licensees (different labels) and the appearance of carbon filament lamps after the introduction of the tungsten filament lamp. It might help collectors to know who was manufacturing lamps after the period of usual interest. The following list was taken from a paperback book titled Incandescent Electric Lamps, Report No 133, Second Series, published in 1939. It was one in a series issued by the United States Tariff Commission.

In the following, the manufacturer's name and location are given as well as the type(s) of lamps made. The type will be noted by TL (tungsten large), TM (tungsten miniature), CL (carbon large) or CM (carbon miniature).

In 1938 the General Electric Company had six plants in Ohio; three of these were lamp assembly plants, two were glass plants and one was a wire plant. In addition, a lamp-assembly plant existed in Massachusetts, Rhode Island, New Jersey, New York, Missouri and California. The Westinghouse Electric and Manufacturing Company (a licensee of the General Electric Company) had three plants in New Jersey. Of these, two were lamp assembly locations in which wire was made in one, and bases were made in the other.

1) General Electric Co. (locations noted above)—TL, TM

2) Westinghouse Electric and Manufacturing Co. (locations noted above)—TL, TM

3) Consolidated Electric Lamp Co. (MA)—TL

4) Hygrade Sylvania Corp. (MA, PA) (Licensee of G.E.)—TL

5) Ken-Rad Tube and Lamp Corp. (KY) (Licensee of G.E.)—TL

6) Chicago Miniature Lamp Co. (IL) (Licensee of G.E.)—TM

7) Tung-Sol Lamp Works (NJ)—TM

8) Birdseye Electric Co. (MA)—TL

9) Everbest Engineering Corp. (NY)—TL

10) Lightmore Appliance Corp. (NY)—TL

11) Slater Electric and Mfg. Co. (NY)—TL

12) Wabash Appliance Corp. (also known as Sun Glo Lamp Works) (NY)—TL

13) American Lamp Works (corp.) (NJ)—TL

14) Atlas Lamp Corp. (NJ)—TL

15) Duro Test Corp. (NJ)—TL

16) Eastern Lamp Co. (also known as Sterling Products Co. and Cosmos Mfg. Co.) (NJ)—TL, TM

17) Elram Lamp Works (NJ)—TL

18) Jewel Incandescent Lamp Co. (corp.) (NJ)—TL

19) Marvel Lamp Co. (corp.) (NJ)—TL

20) Polar Co. (also known as Northern Incandescent Lamp Co.) (NJ)—TL

21) Radiant Lamp Corp. (also known as King Mfg. Co.) (NJ)—TL

22) Wonderlite Co. (corp.) (NJ)—TL

23) Pennsylvania Illuminating Corp. (PA)—TL

24) Warren Lamp Co. (PA)—TL

25) Save Electric Corp. (OH)—TL

26) Carlton Electric Co. (corp.) (NJ)—TM

27) Dura Electric Lamp Co. (NJ)—TM

28) Imperial Miniature Lamp Works (NJ)—TM

29) Vulcan Lamp Works, Inc. (NJ)—TM

30) Herzog Miniature Lamp Works, Inc. (NY)—TL, TM, CM

31) Munder Electrical Co. (MA)—CL

32) North American Electric Lamp Co. (MO)—CL, CM

33) Safety Electric Co. (IL)—CL, CM

A description of the carbon filament lamps manufactured in 1938 can be found on page 93:

"Carbon filaments are the only nonmetallic filaments now used commercially in lamp construction. Carbon lamps are manufactured chiefly with medium or candelabra screw bases, but they are also equipped with special bases such as the German or French candelabra screw bases or bayonet types. Most carbon-filament lamps are made with clear bulbs, only a small proportion having colored or frosted bulbs. Large lamps are manufactured for use on voltages within the following ranges: 20 to 95, 100 to 130, 200 to 275; in 8-1/2 to 120 watts for general lighting, and 50 to 375 watts for therapeutic appliances. Straight-side and pear-shaped lamps are now used to withstand shock, excessive vibration, and rough service. Small quantities of round large lamps are used for illumination and decorative purposes. Tubular lamps are used for heating cabinet baths, and globe-shaped lamps for therapeutic treatments and for hair dryers. Other types are produced for dark-room photographic work, and for special appliances.

Miniature carbon lamps are rated from approximately 2 to 8 candlepower and are used on voltages ranging from 10 to 95, 100 to 130, and 200 to 250. They are used principally as pilot lights in automatic telephone switchboard indicators and in sewing machines. They are also used on waffle irons, Fiske indicators (Navy), the interior of refrigerators, and for Christmas trees and other decorative purposes. Special lamps are also made with indented tops for heating medicinal oils and perfumes."