Streamlight is an American flashlight manufacturer, first incorporated in New Jersey, that produced flashlights using then-new rechargeable battery technology.[1] The Kel-Light company, which Streamlight acquired in 1983 [1], was the first to patent a flashlight battery recharging method in 1973 (US3829676 [2]) but never used it on a marketed product [3]. Streamlight first produced the SL-20, itself covered under a different patent (US4171534 [4]) since it uses a charger which can be simply plugged in, unlike the earlier patents that required the tailcap to be replaced [1], in October 1975 for police use [5]. These duty flashlights were made from aluminum and used a proprietary rechargeable NiCad battery pack which was charged while inside the flashlight with a proprietary charger whose circuitry connected to the battery underneath the external switch. The SL-20 was produced from 1975 until the mid-late 1980’s when it was replaced by the SL-20X model.[1]
Besides police use, SL-20 light were often attached to MP5 submachine guns with specialized mounts for close quarters use, particularly in counter-terrorism units.
Markings:
The prefix-less serial number and “Norristown, PA” on the back shows that this SL-20 was produced between 1978, when Streamlight moved production to Norristown, Pennsylvania, and 1983 when Streamlight acquired Kel-Light. These earlier Streamlights were produced with sequential, purely numeric, serial numbers. After Kel-Light merged with Streamlight, “Norristown, PA / Barstow, CA” was stamped onto the endcap and two letter prefixes were added to the serial to distinguish between the company’s two production lines (“S” for “Streamlight” which was rechargeable, an d “K” for “Kel-Light” which used non-rechargeable alkaline batteries; after this were letters in alphabetical order starting with “A”). [1]
Switch:
The switch can be pushed on for momentary use, or slide forward for continuous use. Improvised weapon mounts, like the balsa wood and hose clamp ones used by Delta Force, can physically actuate the switch. The charger cable connects to a port underneath the switch. Some weapon mounts, like the Laser Products (Surefire) one, use this port for a direct electronic control over the light.
Tail Cap:
Battery Pack:
The SL-20 comes with a rechargeable proprietary NiCad 6V battery pack. It has the same diameter as a D-cell battery, 3 of which can be used instead, for a total of 4.5V, and lower power.
Function:
This picture shows the output with 3 D-cell batteries (4.5V). The full 6V would be even brighter.
Usage Photos:
Streamlight SL-20’s tended to be mounted to MP-5 submachine guns with custom weapon mounts. These were some of the first weapon-mounted lights in service.
British SAS:
Operation Nimrod:
Operation Nimrod was the British Special Air Service (SAS) raid to end the Iranian Embassy Siege (April 30 -May 5, 1980). Taking advantage of the Iranian Revolution and the overthrow of the Shah, and inspired by the hostage taking at the US Embassy in Tehran, six members of the Democratic Revolutionary Front for the Liberation of Arabistan (DFRLA), a Khuzestan separatist insurgent group of Iranian Arabs that wanted to secede from Iran, attacked the Iranian Embassy in London, taking 26 hostages, mostly embassy staff. Khuzestan is a province in southwestern Iran bordering Iraq with an Arab-majority population, which Iraq had been covertly supporting Arab nationalism in to further its geopolitical aims. After a 5 day siege by British authorities, the SAS was authorized by Prime Minister Margaret Thatcher to assault the embassy to release the hostages. The raid was televised, raising the profile of the SAS and becoming one of its most famous actions.
The distinctive “black kit” worn by the SAS on hostage rescue missions was optimized for close quarters battle and is meant to protect the user from fire, smoke, and gas inhalation hazards. The black color was chosen specifically for intimidation purposes. [10][11]
Others:
The SAS tended to mount their Streamlights over the top of their MP-5’s, using the focused beam center to aim. The mount uses a unique Laser Products (Surefire) tape switch component to electronically actuate the switch [14].
There are some late 1980’s photos where they move the light under the handguard, but using a different type of light.
New Zealand SAS:
[16]
Other Commonwealth SAS units also used a similar light mounting system.
US Army Delta Force (SFOD-D):
Some SL-20’s were used throughout the 1980’s, including for Operation Eagle Claw, along with a variety of other companies’ lights. Delta used a unique hose clamp and balsa wood mounting method as well as a British style above the barrel mount.
The balsa wood was used as a spacer and the hose clamps were used to secure the light. The light switch has to be manually operated using this mount.
US Navy SEALs:
The SEALs mounted their SL-20’s onto the side of the handguard, allowing them to use (iron) sights on top.