Covert Edged Weapons History
From The SOE and OSS to Modern Day
There have been many clandestine weapons over the years. Some were excellent ideas with poor materials or execution. For example, at one time, The Tekna "Security Card," which was basically a credit card shaped device with a slide button mounted topside that was thumb-activated to slide a blade out the front of the body. 
A pull with the thumb would then retract the blade into the body. This was a pretty cool thing for the Late 1970s or Early 1980s.
This particular idea reached its zenith with the production of the Spyderco Credit Card Knife. It is a liner lock and has the infamous "SpyderHole" and is simply the best version to date in my opinion. The idea is a very good one and Microtech and SOG Knives have their own versions of the concept as well.
Custom Knifemaker James Piorek makes a high-speed, fixed blade version of the concept. The Credit Card Blade. The first Generation models were simply a credit card sized piece of A2 tool steel with an angled edge on it. After that came refinements to the design with a pocket clip and a dedicated wallet to carry it in for a quick-draw. A further refinement came with the Omega Series Blades in a large wallet/checkbook with a clip on the knife and a Kydex Liner in the wallet. Excellent designs.
My library is rather modest in my opinion. I do have some gems that go above and beyond what most "knife people" or "martial arts people" delve into. For me, these are resources that have given me a greater understanding of all facets of Self-defense.
I admit that I am a "Spy Buff." However, there is more to my interest than that. In my way of thinking, if you study what other people have done and what they were equipped with when they were dropped or otherwise infiltrated into hostile areas where capture meant torture and execution, then at least some of that must carry over to Self-defense on the street.
Of particular interest to me are the weapons issued and improvised by troops in World War One. When the Machinegun made men dig underground to escape the "Devilís Paintbrush," the murderous automatic weapons-fire, men went back to some of the most basic and brutal tools ever known to mankind. The weapons of ancient times. Edged and Impact Weapons.
In the trenches, the shotgun [The Buckshot loaded Pump-Action Shotgun was so brutally effective that the Kaiser formally lodged a complaint against their use] and handgun were most certainly Kings. The various Edged and Impact Weapons, issued or improvised, were the Princes.
If you can dream up some variation of dirk, dagger, stiletto, knife, brass knuckles or blackjack, chances are it was either issued or improvised in World War One for trench warfare.
As you look into World War Two, you see many of these weapons resurrected for use by the British SOE [Special Operations Executive] and the American OSS [Office of Strategic Services]. Not only were they resurrected as concepts/devices, they were improved upon in design and the concealment sheaths were the best available at that time.
In fact, the weapons designs and concealment concepts have stood the test of time. They are in fact timeless.
If we look at some of the incredibly dangerous missions these men and women carried out during World War Two, behind enemy lines, we see a plethora of clandestine weaponry. There are several excellent references filled with Government-Issued "Exotica." Some of them are:
Fighting Knives by Frederick J. Stephens
OSS Special Weapons & Equipment by H. Keith Melton
CIA Special Weapons & Equipment by H. Keith Melton
Clandestine Warfare by James Ladd and H. Keith Melton
The Ultimate Spybook by H. Keith Melton
There are many other books that cover the subject, but these are some of the best as I glance at the bookshelf.
Once you get beyond all of the bugging and communication equipment, cameras, lock picks and the infamous "Escape & Evasion Suppository Kit" [and no, Iím not kidding], you see some of the insight into what weapons-designers have dreamed up to arm our men and women with. These men and women who were sent to hostile areas where sometimes the most effective weapons, firearms, would have never passed any inspection. Meaning arrest, imprisonment, torture and death to our people if they were caught.
Some of the firearms that they were sometimes issued were "last ditch" affairs, and probably less effective than a good edged weapon in trained hands. Single shot, .22 Long Rifle Caliber weapons disguised as cigarettes and cigars for example, for point blank firing. Along with the infamous "Liberator" and later version of the Liberator, the "Deer Gun" single shot pistols, and "The Stinger."
The edged weapons, garrottes and various bludgeons always caught my eye as well as my interest though.
There are many different edged weapons in this category, with the Fairbairn-Sykes Dagger in a forearm or leg sheath being one of my favorites. Not because I feel it cannot be "bettered" by modern edged weapons, but because it was the epitome of edged weapons then for the intended purpose. Clandestine Warfare.
Robert S. McKay writes in "Modern American Fighting Knives," the following;
"During a recent conversation with Col. Rex Applegate of the OSS, he explained Fairbairnís approach to the use of the knife very clearly. ĎWhenever a new civilian or military trainee arrived at Area B (the Close Combat Section of the OSS training facility at Camp David, Maryland), Fairbairn would engage him in innocent conversation at armís length. Once Fairbairn felt his subject to be off-guard, he would reach casually into the front pocket of his British battle dress, and with lightning speed, draw his knife and put it to the throat of the unsuspecting trainee.í"
On the standard Fairbairn-Sykes Commando Dagger Sheath, there are leather "ears" or tabs with pre-bored holes for ease of sewing the sheath into a large or modified pants pocket, or even on the outside of clothing for those that did not have to worry about concealment. 
This simple and very effective method of securing a sheath onto clothing was repeated with the Lapel and Thumb Daggers.
There were three basic types of sheaths for the Lapel, Thumb, Sleeve ["Nails or Bodkins"] Daggers ;
1. Leather Sheath, pre-bored holes for ease of sewing. 
2. Leather Sheath, Forearm/Wrist Leg/Ankle Strap. 
3. Leather Sheath, with a pre-cut button hole "slit" for attachment to the inside of clothing on a button. 
Likewise, the full-sized Fairbairn-Sykes Dagger had the standard sheath and one for use on the forearm and leg.
There was also several different versions of the F-S Commando Dagger, all were smaller. One was the "3-4 F-S Fighting Knife" that was smaller and was supplied with a Forearm/Wrist Sheath and Strap.
There were incredibly small versions as well, Miniature F-S Daggers that until recently, they were thought only to be "Presentation Models" or fancy letter openers. But apparently they were in fact issued, carried and used and were much preferred over the Lapel and Thumb Daggers as they had a better grip and a small guard.
In the Spring 1996 Issue of Tactical Knives Magazine, Leroy Thompson wrote an excellent article. "The Miniature Fairbairn-Sykes, At Last, The True Story!"
There were pictures of the true Miniature F-S Daggers, the 3/4 and 7/8 F-S Daggers and two very interesting Miniatures, one had a grip that screwed in half to reveal a place for the infamous "L" Pill, "L" for "Lethal," Cyanide. Another had a spool of wire around the grip for use as a Garrotte.
There were other knives that were in fact issued. In World War One, there were several different "Trench Knives" with either double edged daggers or triangular blades in tandem with brass knuckles. 
These were no doubt used and there are pictures of these knives in WW2. There is a lesser known "Knuckle Knife" known as the "Clements BC-41." 
With the fingers through the brass knuckle grip, the bladeís edge faces [up] the user. This was clearly for cutting the throat of a Sentry from behind when the knife was in forward grip. For those well-versed in use of reverse grip, it would still function well today in extreme close quarters combat, using it edge-in.
Robbins of Dudley produced quite an array of "Knuckle Knives" ["Deathís Head, the knuckles somewhat resembled a skullís eyes] as well as Push Daggers where the brass or aluminum knuckles had the blade coming out the front. Brutal and effective.
And this is not an all-inclusive list of edged weapons either. There were some extreme examples of covert weapons/edged escape tools as well.
Just a few of examples...
In the world of the Cheating Gambler, there is a device known as a, "Jacobís Ladder." This was a spring-loaded or otherwise activated, folding [accordion] type of extension that could be hidden up a sleeve so with very little [trained] movement, a Cheat could push a hidden card into his palm during a card game.
The British SOE took this idea and constructed a leather, strap on gauntlet that could be concealed by a sleeve but in the end, the design was too bulky. Instead of pushing a card into the hand of an SOE Operative, it extended a five inch blade, similar to a double edged Lapel Dagger for immediate use. This device appears on Page 31 of Keith Meltonís excellent book, "Clandestine Warfare."
There are also examples of "Hairpin Daggers, Ring Knives [Tire Slashers] and Sharpened Fingernail Files."
Another version of the Lapel Dagger was heated and formed so it matched the arch of the foot and a specially made leather sheath was made. The shoe could be removed and the knife draw for use during an escape. This is pictured in the same book.
This could be used with another specialized leather "sole" in the other shoe that had a zippered compartment that could hold five Gold coins. With these, the Operative could take the Professional-grade Passport-sized photographs issued to him and pay for counterfeit identification, Passports, clothing and perhaps food or other equipment, transportation, etc.
The OSS "Frisk Knife," meant to be missed during a quick, pat-down search was apparently patterned after a commercially available German Throwing Knife of that era.
Enter the 1970s
With crime reaching all-time high levels, Citizens began to scramble for anything that could be carried and used for Self-defense. There existed at the time in magazines such as "Soldier of Fortune," these hardcore advertisements on the latest concealed Edged and Impact Weapons. Ranging from brilliant to almost perfectly stupid.
Classic brass knuckle patterns were sold as, "Brass Paperweights," the concept of an SOE/OSS "Spring Cosh," a telescoping set of coil springs with a metal head was marketed by a German Firm in two sizes, "Sipo" and "Blitz." Later, a Japanese Firm would market the "Kiyoga Baton."
Into the 1980s
The 1980s literally exploded with these sorts of covert weapons. Major Custom Knifemakers like Pat Crawford began to make their own versions of the SOE/OSS Sleeve Dagger. Mr. Crawford calls his renditions "Devil Darts." 
Mr. Crawford also designed a neat little device called a, "Push Pick," this device could have the threaded spike screwed into the housing and the blade was concealed and the whole unit used as a fistload, or it could be screwed into one end to form an icepick, or into the center to form a Push [Dagger] Spike. 
Some of the best covert weapons were made by what is now one of the largest knife companies, Cold Steel, Inc. Lynn Thompson, the Owner of Cold Steel, had several edged weapons that were marketed as Self-defense Weapons,  and the thought that went into them was great. They used timeless designs with some more modern materials.
These small, ingenious weapons would become the springboard, along with the infamous Cold Steel Tanto, that would launch Cold Steel, Inc. into the forefront of The Knife World.
Cold Steel, Inc. was possibly the first Manufacturer that produced a Neck Sheath, long before any Manufacturer discovered Kydex, Cold Steel, Inc. was using leather sheaths modified for this purpose.
But the innovation did not stop there. The whole "Urban Series" of edged weapons from Cold Steel had wonderful carry systems that were probably misunderstood when they were released.
The Urban Skinner was a single-edged Push Knife, Cold Steel took the Classic "Gamblerís Knife" and using modern materials, created what is, to this day, one of the best Self-defense weapons available in my opinion. Later, a slightly larger and double-edged version, "The Terminator," was introduced. Both had Kraton covering the "T" handle and were excellent weapons.
The Urban Pal was a smaller, single-edged Push Knife without the Kraton covering the handle. Many sheaths were produced for it. A wallet sheath, a neck sheath, a keychain sheath  and a sheath with velcro on the back. 
Clearly stated in an early Cold Steel catalog is the whole idea of sewing a piece of velcro onto the back of a lapel, or some other area, and then attaching the sheath in this manner. The Lapel and Thumb Dagger Sheath, in modern form. 
This idea was also used with the single-edged Urban Hunter and the double-edged Urban Shiv. Velcro on the back of the sheath so the matching piece of velcro could be sewn behind lapel, tie, or anywhere in clothing. 
A separate piece of leather with a matching piece of velcro on one side and an excellent belt/boot clip on the other could be placed on the sheath for different modes of carry. 
A picture of the Urban Shivs and Pals. 
Al Mar Knives once marketed a close copy of the OSS Escape Tool under the name of "The 4X4 Tool." Also of note was a chisel ground, double-edge Comb Dagger named "The Wild Hair." 
Black Cloud Knives produced Laci Szabo Designed "Kitten Claw" ring knife, which is conceptually very close to the OSS Tire Slasher that was issued in a leather pouch type neck sheath, which I had reproduced as a button hole sheath by a Sheathmaker. 
This picture is a chisel ground, double-edge Lapel Dagger made by Knifemaker Bill Siegle and sheathed by the same Sheathmaker that usually does my Custom Work. 
There will be a shorter article on how some of these edged weapons were supposed to be used and how they can be used.