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WWII Emergency Signal Mirror

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I have put together an article on the history of the emergency signal used by the US air services.

The United States WWII emergency signal mirror:

The use of reflective surfaces to direct sunlight goes back as far as man was able to cast metals.It is not exactly clear when the use of reflective devices were adopted for emergency use but we can be almost certain it has a long history in the navies and armies of the world.Before radio communication the signal mirror was a valuable communication device easy to use and inexpensive.The applied use of signal mirrors, polished steel and plated metals,was not fully utilized till for rescue purposes by the United States armed services till WWII,first used by the united states navy,merchant marine then the army air corps.It's early history is not well documneted among the US aviation services with vague references showing up here and there on unit and individual levels.The united states navy was the first to standardize the mirror as an implement of emergency rescue equipment and to become a component part to all life boats,life rafts and emergency equipment containers as wel as an optional piece of pilots personnal equipment.The importance of the signal mirror air sea rescue purposes was not fully recognized by the us navy and AAC until the Rickenbacker search & rescue in 1942.The survivors were able to see searching aircraft but unable to signal them in which a simple inexpensive mirror would have been able to allow a possible contact.Army air corp raft kits at the start of WWII did not include an emergency signal mirror, bureau of aeronautic kits did.



In the 1930's the bureau of aeronautics developed a round signal mirror as a standard piece of emergency equipment.The earliest version was made from chromium plated brass later changed to chromium plated sheet metal, due to critical materials rationing, then coated coated with a lacquer finish to resist corrosion.This mirror is 4" in dia. contained in chamois case the original version had a 1/8" hole near the edge for sighting purposes later by 1943 it was recommended to all activities that a 3/8" hole be drilled in center for sighting and the 1/8" hole be used for a laynard to prevent loss.The mirror and case were manufactured by the Naval Aircraft Factory under part number 214298-1.This mirror was included as standard equipment in all rescue kits in use by the buaer entering WWII.As the war spread across the world many aviators went down due to nemy action and accidents.It was soon found that the chromium plated mirror had many draw backs it corroded easily from long exposeure to slat water,the sighting hole was found unsatifactory and had a tendency to wrap due to high humid heat.This mirror was eventually replaced by the buaer spec. M-580 emergency signal mirror in 1943 though the stayed in service till the end of the war.The one from my collection I got from a naval vet himself and told me that this mirror was issued to him and all others in boot camp, he joined the navy in november 1944.This early mirror was the first generation mirror out of three developed by the buaer in WWII.

The story of the second generation mirror begins in september 1942 with a meeting of representitives from the United States Coast Guard, Office of Stratigic Services and the National Inventors Council who came to the National Bureau of Standards to devise a more suitable signaling mirror to be included in rescue and emergency equipment.Experiments from oct. 1942 through march 1943 proved that a tempered glass mirror to be the most effective over stainless steel and plated mirrors.The tempered mirrors were provided by the General Electric co. made from evaporated aluminum on tempered glass.Electric companies use mirrors anywhere that visible light must be cooled through reflection these mirros must be very tough to handle extreme conditions.the tempered glass mirrors used during the tests incorperated a design by larry L Young from the Bureau of Standards and W.M. Potter from the General Electric co. based on a rearsight sighting hole in the shape of a cross to allow a wider field of view in lieu of a round hole.Another mirror example was presented at the tests by a man named Charles M. Learned of the retroreflective type.Another type tested was one of Royal Air Force origin the fore sight method which was not very favorable to the US.

The bureau of aeronautics adopted the design by the Genral Electric co. incorperating the rearsight method by Young and Potter under buaer specification M-580 being standardized in june 1943.Under this spec. more tests were conducted on the demensions of mirrors for the best reflective properties but maintaining a compact size,this size being the 4"x5".Studies within the buaer pointed out that 7 out of 10 individualscould not use a signaling mirror properly so under spec. M-580 it detailed a layout for printed instructions on back.Also known as the ESM/1 which is actually the General Electric co. nomenclature and not military related at all though the mirrors are printed with ESM./1 on instruction side.The correct nomenclature to the buaer is M-580 or tempered glass type.The General Electric co. was the only contracter awarded manufacture of the M-580 signal mirror.These mirrors can resist salt water corrosion and a drop up to five feet from the ground with a visual range up to 10-20 miles on a clear day.These mirrors caome packaged in a waterproof foil lined paper.

Third Generation: During tests conducted in oct. 42 Charles M. Learned presented his invention of a retroreflective type mirror which was more effective that the tempered glass type being much easier to aim than the rearsight.Why the buaer did not adopt the learned design at this time is not known probably due to the complicated nature of manufacture leaving the glass mirror more cost effective to manufacture.Eventually the buaer did adpot the learned design under spec. M-580A,exact date of amendment is unknown at this time with quantities being delivered by the middle of 1944 eventually replacing the tempered type.Measuring 3"x4" the m-580A used a red reflector button set at a 30 degree angle behind a clear window to aim mirror a much more effective method in rough seas compared to the rearsight .During tests between the tempered type and learned type mirrors showed the average number of flashes observed per minute was much greater from the learned at an average of 34 compared to 14 from the rearsight method.Under amendment A eight orange reflectors were provided on back for night use.The buaer nomenclature is the M-580A,learned type or reflex button type.This mirro comes packages in a waterproof foil lined kraft paper with instructions printed on one side.When the mirror is removed from wrapper it is sealed between two tin halves one half has printed instructions and the other says warning do not bend flap.It is also common to find these with instructions on both halves.The M-580A was used up and into the vietnam war being rpalced by the Mark 3 signal mirror.


The Army Air Force adopted the General Electric mirror,ESM/1, in sept.1943 under specification 40653.The AAF did not include an emergency signal mirror in any emergency kits as standard equipment during the pre war and enter war years.By the middle of 1944 the ESM/1 mirror was added to many existing and newly developed emergency and life raft kits.there are slight variations between the the M-580 and 40653 spec. mirrors on the instruction side.The AAF mirror is packaged in a waterproof foil lined kraft paper with an outer labeled cradboard carton also packed in a labeled kraft paper.


All pictures presented are from my collection

this photo is of the buaer first generation mirror



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oops i left out part of text.

At the time the AAF standardized the ESM/1 signal mirror they were making an amendment in spec. 40653 for a mirror of reduced size to be incorperated in the C-1 emergency sustenence vest.The only change was demensions from 4x5 to 3x5 inches.This new size mates perfectly with the emergency parachute ration which are included in the same pocket on the vest.The original mirror design for the c-1 vest was a rectangular stainless steel mirror in canvas case which was dropped in lieu of the ESM/2 emergency signal mirror,very little info is available on theis early mirror.This new tempered glass mirror spec. 40653A retains the same spec. 40653 in period component listings.This mirror only seems to be issued with the C-1 vest and not included in any other kit probably due to the size of other kits able to incorperate the larger ESM/1.the ESM/2 only seems to be issues in a yellow kraft envelope since the mirror is pre assemble in the c-1 vest from the factory and does not need an outer carton which would add bulk.

The last mirror developed by the AAF during WWII was the type B-1 sepc. 41063 a late war development using a new material called scotchlite,a highly reflective material commonly used on oars at that time.this new mirror is of the retroreflective type which has proven to be more effective in emrgency situations than the rearsight method.Developed too late to actually see service but deserves to be mentioned.

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  • 2 months later...
  • 8 months later...

I had to be absent last months at the USMF but it is a pleasure to be back in the topics Dustin is Guru. I may add only that in 1943 the BuAer published small instruction how to use signal mirror 1st type. I am posting it below.






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  • 6 years later...

I have put together an article on the history of the emergency signal used by the US air services.


A wonderful resource!




Here's a WW2 US signal mirror training video produced by the OSS in August 1943, showing how to use the General Electric ESM/1 "cross-in-glass" signal mirror:


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  • 1 year later...

This 1949 article in Naval Aviation News[1], while focused on the Mark 3 mirror that supplanted the WWII mirrors, summarizes the WWII history, and adds some detail on an experimental WWII (May 1944) signal mirror that did not make it into production.

NEW MK-3 SIGNAL MIRROR OUT ( Naval Aviation News, June 1949, p. 35)


BuAer Airborne Equipment division is procuring a new and improved signaling mirror for inclusion in multi-place life rafts and PK-2 survival kits carried by pilots.

Fifth and latest of the line of signaling mirrors developed since the start of the war placed much emphasis on ocean survival, the new device will replace all existing mirrors which do not have reflex sighting. Three years of testing went into the design before it was accepted.

The new mirror is made of double-laminated tempered and annealed glass and is so tough it will resist heavy usage without breaking. Sighting is done as with several other of the signaling mirrors – through an aperture in the middle of the mirror. A stainless steel screen coated with Scotchlight produces a gleaming "point" for the downed pilot to aim at a plane overhead or distant ship to catch their eyes by flashing sunlight.

The Navy started the war with a simple signaling mirror made of stainless steel with a plain hole in the middle. The next one brought out was the Mk 1, featuring a plus sign in the middle for sighting. An experimental model, never produced, came next. It had a hinged inset in one end for sighting but its plastic construction did not stand up in the water so the Mk 2 mirror was brought out. This featured a black metal casing for a mirror and a fixed-hinge sighting reflector. The new Mk 3 device, with a range of 10 miles or more, replaces these.





I take issue with the "simple signaling mirror made of stainless steel with a plain hole in the middle" - as discussed above, the early war mirror was chromium plated brass with no central hole.


The "Mk 1" is the ESM/1, and the "Mk 2" the M580A.


The experimental signal mirror described matches US patent 2,467,165 filed by Stimson in May 1944 : M580A: http://www.google.com/patents/US2467165 - compare the patent figure below to the one above. Both the patent and the article describe a plastic mirror with (implicitly, in the article) an adjustable hinge.




The "MK3" signal mirror depicted appears to be the BuAer Spec. 23M5(AER) model with the orange-on-black decal on back of gold-tinted glass, as seen here with a similar variant Spec 41063 B-1 model: "B-1 and Mark 3 Signal Mirrors" https://www.flickr.com/photos/signalmirror/16200655777/

in this gallery of B-1 Signal Mirror photos: https://www.flickr.com/photos/signalmirror/sets/72157650104319419



[1] "NEW MK-3 SIGNAL MIRROR OUT", Naval Aviation News, June 1949, page 35.


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A lot of us had those B-1 looking things.

Scrounged from somewhere. Never actually issued.

Might have come from pilfered Air Force stuff, like the pin flares.

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[1] "NEW MK-3 SIGNAL MIRROR OUT", Naval Aviation News, June 1949, page 35.


??? For some reason, the link above is offline, and I don't see how to edit my post to provide an alternative link.


Use this link from the Internet Archive instead:


or, if you just want to download the June 1949 issue of Naval Aviation news in isolation:


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I have an ESM-1 that my father used for shaving while he went camping. I use it when I'm cutting my hair at home!

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