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Kel-Lite was the first heavy-duty aluminum bodied flashlight, which became popular with law enforcement agencies due to its heavy construction. They were designed to be carried in place of a police baton and also provide light.
The Kel-Lite was a highly-durable, weather- and shock-resistant flashlight (UK: torch), made of heavy 6061-T6 aluminium. It was developed in 1968 by Donald Keller, a Los Angeles County Deputy Sheriff, who was tired of the lack of durability of the generically available, cheap metal flashlights of the day. It was later (1973) redesigned by Norm Nelson into the modern version with a battery charger, adjustable lens, baton lights, push button switch, and in three sizes (DKL (D-Cell Kel-Lite), MKL (Medium Head Kel-Lite), SKL (Small Head Kel-Lite)), and penlight versions. The company merged in 1983 with Streamlight. Kel-Lite had manufacturing capability and Streamlight a marketing team.
The first Kel-Lites were made in San Dimas, California in 1968. Then the company moved to Covina, California in 1970 as demand increased, and on to Barstow, California in 1973 to a larger facility with a full service machine shop, plating, assembly line and shipping department. Donald Keller left Kel-Lite in 1972 and continued designing lights for Brinkmann, ASP, and Maglite.
Surviving Kel-Lites are still in use worldwide, with the final design by Norm Nelson (Excalibur) made by Streamlight into the early 1990s. A similar model, also designed by Keller, is still being sold as the Brinkmann "Legend" series of flashlights.
Designed by Don Keller from 1969-1972 included the Large head KL model, The small Head SKL and the C cell CPL models.
Locations included San Dimas & Covina. Plastic slide switches. Later models of the 1st generation lights were also produced for a short time in Barstow. San Dimas was stamped on the barrel behind the switch. Covina & Barstow were stamped in the tail cap.
Switch design by Norm Nelson from 74-83 same head styles as above and added a medium head. Also included the Baton light and Stud Light. Metal slide switches. Produced in Barstow, CA.
Designed by Nelson & Streamlight, 1983 until approx. 1985. Medium head only with push button switch. Produced in Barstow, CA. and Norristown, PA. Kel-Lite attempted to get into the rechargeable market with a tail cap charger, only a few were actually sold.
The Kel-Lite was intended as a replacement for the baton carried by police officers. The series of Baton Light models (available in various lengths from 18 to 26 inches) were designed by Norm Nelson in 1973 as a direct replacement, which would fit into a standard baton ring on the officer's belt.  Kel-Lites were available in sizes ranging from a model using two "1/2 D" cells (together the length of one D) to those using 7 D cells, and any size in between, as well as C cell models. A total of 49 different models were made.
Prior to the Kel-Lite, flashlights were relatively fragile and undependable, usually made either of molded plastic or stamped sheet metal. Dropping one would usually break the bulb, and dents would often lead to frequent replacement. Keller designed the Kel-Lite to be robust. Salesmen trained by Keller would demonstrate this for public safety customers by pounding large nails into a block of wood, while the light was operating. Other demonstrations included throwing the light as hard as possible across a concrete parking lot, or turning the light on and putting it into an aquarium and driving over it with a truck. Nelson also produced a flashlight targeted for the truck driver known as the Stud-Lite, which was a Kel-Lite flashlight with a different name, and anodized finish. This model was also very popular and sold in truck stops, truck dealerships and parts houses.
The success of the Kel-Lite led to the rise of competition, primarily Maglite and Streamlight, who improved on Keller's basic concept. Streamlight opted for high-output models using rechargeable battery and halogen bulb technology. Maglite developed an improved switch and a variable-focus system, allowing a single light to be used for a high-intensity flashlight or wide-angle lantern. Mag-Lite later developed their own high-output rechargeable, as the police market converted entirely to that style of flashlight. A decade later a new company, Laser Products, miniaturized the tactical flashlight with their SureFire series.
These more advanced and mass-produced products eventually took over the market. Kel-Lites were one of the more durable makes and large numbers are still in use today. They remain popular on the used market both as working flashlights and collectibles. A Kel-Lite torch was also mounted on the High Standard Model 10B bullpup shotgun.
- David E. Steele, The Modern Weapons of Law Enforcement, Black Belt, July 1984 Vol. 22, No. 7 ISSN 0277-3066 pages 28-29