A Short History of the U. S. Army M-1950 Lensatic Compass

The history of the U. S. Army Lensatic Compass is relatively unknown. Yet, the origins of the compass are interesting.

The U. S. Army lensatic compass is an iconic land navigation device. Its decades of use by the U. S. Army, Air Force, Marines, and SOF make this compass one the best ever produced. Furthermore, the history of this piece of military gear is relatively unknown. Much like the history of the Air Force Survival Knife, the background about the military lensatic compass is minimal. The compass is undoubtedly not the first to employ the lensatic sighting system. However, it did standardize the use of the lensatic sighting system. Yet, the origins of the compass are interesting.

Origins Of The Lensatic Compass

The Schmacalder Compass

The current version of the U. S. Army Lensatic Compass finds its roots in similar compass styles in use before World War II. The current lensatic compass is an evolution from the older hand-held sighting and surveyor’s compasses in use during the 19th and early 20th centuries. For example, on March 5, 1812, Charles Augustus Schmacalder, an optician and instrument maker, received a patent for his prismatic sighting compass design from the Royal Patent Office in London. His design is the first to feature a folding prismatic sighting mechanism that is similar to the one on the current military lensatic compass. The Schmacalder Compass was the standard prismatic compass in use by the British Army throughout the late 1800s and early 1900s before World War I.

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The Schmalcalder Compass

The Verner Compass

Later, Colonel William Willoughby Cole Verner of the British Army improved Schmacalder’s design for a pocket compass. Verner’s compasses are sometimes referred to as marching compasses. These marching compasses were used for moving mounted and dismounted infantry units across the late 19th-century battlefield. Verner’s compasses are the first to look more like the modern military lensatic compass. It had a folding lid, folding wire sight, and folding prism eyesight. They were carried in a leather pouch that was attached to a British officer’s waist belt. Verner’s compass became the standard pocket field compass for the British Army throughout World War I.

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The Verner Marching Compass

The U. S. Army Needs A New Compass

The Pocket Watch-type Compass

By contrast, the pocket or hand-held compasses that were in use with the U. S. Army during World War I resembled modified pocket watches. The reason for this phenomenon is that most of the compasses in use by the U. S. Army during that era were manufactured by watch companies. Examples of such compasses are the Waltham Watch Company Pocket Compass. Cruchon & Emons of London and the Plan, Ltd of Neuchatel Switzerland also made pocket compasses for the U. S. Army during World War I. The C&E and Plan company pocket watches are early attempts at a mirrored pocket sighting compass.

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Waltham Pocket Compass

The M-1938 Lensatic Compass

Undoubtedly, U. S. Army service personnel became aware of the Verner prismatic compasses while serving with their British counterparts in World War I. The Army authorized research and development projects to develop a new compass at the request of the U. S. Army’s Infantry School in Fort Benning. The first of these R&D projects for a new compass was issued on March 21, 1928. The agency responsible for the research and development of compasses for the U.S. Army, at that time, was The Engineering and Topographic Laboratories at Fort Belvoir, Virginia. Additional research projects were issued until 1938. Special Project 280 (SP-280) was authorized on October 21, 1938, to find a suitable commercial lensatic compass for the Infantry that met the Infantry School’s requirements. The Engineer Board did not discover a commercial compass that met the standards published by the Infantry School. However, two companies, The W. &L. E. Gurley Company and The Taylor Instrument Company offered to make new compass prototypes based on the Infantry School’s requirements. After the testing and modifications of their compasses, they were recommended for procurement in 1940. Both manufacturers supplied compasses to the U. S. Army during World War II. Their compasses were designated as the M-1938 Lensatic Compass.

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M-1938 Lensatic Compass

The M-1950 Lensatic Compass

Liquid Filled Dampening

The U. S. Army continued to suggest improvements to the M-1938 lensatic compass throughout World War II. For example, there were several attempts to solve the mechanical dampening problem with the lensatic compass. In short, they were attempting to find ways to keep the compass needle from oscillating when taking a bearing. Reducing oscillation of the needle helps to gain a more accurate reading when taking an azimuth and bearing for land navigation. A liquid was commonly used for dampening in the lensatic compasses through most of World War II. The use of liquid dampening was a better option for the technology of the times. However, experimentation with the dampening process continued throughout the war.

Induction Dampening

According to Pennington, the Superior Magnetic Corporation discovered how to dampen the lensatic compass without using liquid through the employment of the induction dampening principle. Induction dampening uses the electromagnetic field to control needle oscillation instead of liquid. The compass well was made of copper which allowed the magnetic field to act as a dampener on needle movement. The company’s effort resulted in the lensatic and wrist compasses incorporating induction dampening by the middle of 1945. These new compasses were quickly procured and issued to military service personnel in the waning days of the war.

Standardizing The Lensatic Compass

In 1947, there was a renewed emphasis on developing a more standardized lensatic compass. The push for a more standardized and improved compass was part of a more extensive program of standardizing equipment across all of the services after World War II (see my article on the Air Force Survival Knife). The Taylor Instrument Company and the Brunson Instrument Company submitted prototype compasses that met the published specifications and standards by the U. S. Army. The Brunson compass was accepted, and the project for developing a new standardized lensatic compass was completed in 1952. The new lensatic compass was designated Compass, Magnetic, M-1950.

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The Brunson Lensatic Compass

The Modern U. S. Army Lensatic Compass

The M-1950 Lensatic Compass is a design that is still in use by the various military services of the United States Department of Defense. Improvements and modifications have continued on the compass. However, the basic look, construction, and employment of the compass has mostly remained unchanged over its nearly seventy-year history. The government contract to supply the lensatic compass to the military has changed hands over the life cycle of the compass. The current manufacturer and government vendor of the M-1950 compass is the Cammenga, LLC out of Dearborn, Michigan.

The Cammenga Lensatic Compass

Cammenga produces two versions of the M-1950 compass for the U. S. Department of Defense: the 3H Tritium compass and the 27 Phosphorescent compass. The only real difference between these two compasses is the material used to meet the self-illuminating features required by the military standards. Cammenga also offers the compass in two magnetic orientations: northern hemisphere (needle points to the magnetic north pole) and southern hemisphere (needle points the magnetic south pole).

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Cammenga 3H Lensatic Compass

Concluding Thoughts

The U. S. Army Lensatic Compass has proven its value over the last sixty years. Its development can be traced to the first prismatic and pocket compasses of the nineteenth centuries. The endurance of the design and construction of the current lensatic compass is a testament to the innovative engineers at the Brunson Instrument Company. Cammenga carries on the high standards for the construction of the M-1950 compass. The M-1950 Lensatic compass is an essential piece of gear for those heading to the outdoors. It requires some practice in using it, especially in land navigation. However, one will not be disappointed by the U. S. Army Lensatic Compass.

For additional information see the following articles:

https://olive-drab.com/od_soldiers_gear_compass_lensatic.php.

http://northingeasting.blogspot.com/2012/05/history-revealed-origins-of-army.html.

A Short History of the Air Force Survival Knife

The genesis of the Air Force Survival Knife goes back to the 1950s at the dawn of the jet age. Here is the basic history of this knife.

June 21, 2018

Many of us have been exposed to the fixed blade knife known popularly as the Air Force Survival Knife. We have seen it in outfitter stores, marketed on the internet, and may even have owned one. Possibly, some may have had one issued to them while serving in the military. This knife has been around for many years. It used to be a standard piece of gear for anyone, including backpackers, who was a serious outdoorsman and wilderness adventurers back in the 1970s and 1980s, before the Rambo movies made popular the Rambo-type survival knife. I became curious about the background and history of this knife about a year ago. It was enlightening to discover that there is very little information available on the background and origins of this knife. Most of the information that I have collected about the knife comes from blogs and knife forums on the internet. After vetting the information against the published government standards for this knife and the government procurement process, what emerged was a unique story of an iconic knife that has found its way from the military to the civilian outdoor world and into the hearts of many owners and users.

Origins Of A New Survival Knife for Military Aircrews

Robin Olds Survival Knife2The genesis of the Air Force Survival Knife goes back to the 1950s at the dawn of the jet age. The U.S. Defense Department published to private industry requirements for a standardized fixed blade knife to issue to pilots and aircrews of the various service branches. Before this requirement, knives of several types were procured by the individual branches of the military and dispensed to their members. By contrast, the current DoD procurement process is much more refined and regulated. Thus, the current standards, methods, and procedures were not necessarily applicable to the procurement process that brought this knife into existence. As such, finding a definitive history of the development and procurement of this knife is difficult to reconstruct. It is assumed that such information resides in the archives of the companies that have manufactured the knife as well as the files of the DoD. However, based on the information that I have collected, vetted, and coupled with my own experience with the DoD procurement and testing process, here is the basic history of this knife.

The story of this knife seems to begin in 1953, when the DoD announced to private industry their specifications for a standardized survival knife for pilots to interested vendors in Military Specification MIL-K-8662 (16 October 1953). Companies interested in gaining the government contract received these requirements and submitted proposals for consideration based on those requirements. As the development and testing process began to take shape, updates to the original specification documents were published. The 1954 update calls for the knife to have a sharpened clip point blade and an additional rivet to the sheath. That same year, the Marble-Arms Corporation (now known as Marble’s®) began work on designing their prototype for the survival knife based on the government specifications. In 1957, the Marble-Arms Corporation submitted to the U.S. government a design based on their Ideal Hunting Knife design. This design was accepted, and the military specifications documents were updated to reflect Marble’s concept in MIL-K-8662A (04 November 1957). This military specification document would become the standard for further improvements and changes to the pilot survival knife throughout the years.

Marble produced several thousand knives for field testing and delivered them to the U.S. Air Force between 1957-1959. After the completion of testing and bidding competition between Marble, Camillus Cutlery, and the Ontario Knife Company (OKC), Camillus was awarded the contract to supply the new Jet Pilot Survival Knife (JPSK) to the Department of Defense instead of Marble. Camillus produced the knife with a 6-inch blade from 1959-1961. In 1961, updates to the military specifications called for a 5-inch blade. Camillus produced the Jet Pilot Survival Knife with a 5-inch blade from 1961-2006. It appears that in 2006, Ontario Knife Company became the current vendor to the DoD of the Jet Pilot Survival Knife under the National Stock Number (NSN): 7340-00-098-4327. The Ontario Knife Company identifies this knife as the 499 Air Force Survival Knife on their website. Additionally, OKC is the only company selling this knife commercially.

The Air Force Survival Knife Introduced to the Commercial Market

The Air Force Survival Knife was introduced to the commercial market by Marble after not being awarded the DoD contract to supply the new survival knife to the military. The reason behind Marble selling their knife to the general public was due, in part, to pre-maturely manufacturing several thousand knife blades and parts in advance of learning who would be awarded the government contract to supply the knives to the military. To recuperate some of the money that they had spent producing blades and knife components, Marble offered a civilian version of the knife to the public in 1961. Their commercial version of the survival knife had a polished blade instead of a subdued or blued blade, brass guard, and polished pommel. These knives became popular with outdoorsman. Later, after service members began returning from Vietnam, the military-grade issued knives began to be seen on the market. Currently, the military-grade Air Force Survival Knife is only manufactured and sold by the Ontario Knife Company.

Design Features for the Air Force Survival Knife

The primary document that describes the various features of the Air Force Survival Knife is Military Specification MIL-K-8662 (16 October 1953). Over the decades, this document has been updated. The current edition of this document is Aerospace Standard SAE-AS-8662. However, the essential features of the knife have remained constant throughout the life of the knife. What are the unique features of the Air Force Survival Knife, as outlined in the U.S. Government specifications?

Basic Description:

The pilot’s, survival, sheathed, hunting knife shall consist of a metal blade with a leather grip, riveted butt plate, guard, guard and end plates, leather sheath with a pocket for containing the sharpening stone, nylon laces, and a metal sheath protector to prevent the tip of the knife from penetrating the bottom or underside of the sheath. The intended use of the knife is for pilots as required in survival situations.

The Blade:

  • The blade is to be a “through tang” blade blanked from AISI 1095 steel conforming to MIL-S-8665 Steel Bars, Carbon, AISI 1095, Aircraft Quality.
  • The blade will be tempered to a Rockwell Hardness of C50-C55
  • The cutting blade is to be 5 1/8 inches long and 3/16 inches thick.

The Sheath:

  • The sheath shall be made of leather in compliance with Federal Standard KK-L-271 Leather, Cattlehide, Strap, Vegetable Tanned.
  • The sheath leather shall be 8/64-inch-thick
  • The sheath welt shall be 3/8-inch-thick and 2 ½ inches in length.

The Handle Grip:

  • The grip will be made of leather in compliance with Federal Standard KK-L-165 Leather, Cattlehide, Vegetable Tanned and Chrome Retanned; Impregnated and Soles.
  • The leather for the grip will be cut into washers, 1/8 inch in thickness.
  • The leather will be treated with para-nitrophenol fungicide.
    • Paranitrophenol fungicide:
      Paranitrophenol was first registered in the United States in 1963 as a fungicide incorporated into leather products and hides as a preservative. A second fungicidal product was registered in 1967. Both products contained a second active ingredient, salicylanilide. However, the registrations for all registered products containing salicylanilide as an active ingredient have been canceled. Currently, one pesticide product is registered to contain para-nitrophenol as an active ingredient. This registration, granted in 1980, is for use of paranitrophenol as a fungicide incorporated into leather for military use, at a concentration not to exceed 0.7% on the basis of dry finished leather weight. In 1983, this registration was amended to add the use of the product for incorporation into cork insulation for military use.

The Sharpening Stone:

  • The sharpening stone shall be fabricated from silicon carbide, grain size 280, hardness P, vitrified bond.
  • The sharpening stone size shall be 3 inches long, 7/8-inch-wide, and 1/4 inch thick.

Some Comments on the Design Features of the Air Force Survival Knife

The Air Force Survival Knife was designed to meet a particular requirement for the military. As such, this knife was not intended as a frontiersman or bushcraft knife, per se. The design features for this knife came about through various inputs from servicemembers, survivability researchers, and training developers. Moreover, the requirement for having a standard survival knife for pilots and aircrews across the DoD was due to economic considerations and budgeting constraints at the time which fostered standardization across the military services. Furthermore, standardization of equipment reduces costs upon the logistical system. These influences upon the procurement system tempered the DoD design features of the knife.

Additionally, the jet age in military aviation increased the number of gear pilots and aircrews had to carry on their flights. Thus, finding ways of reducing the bulk of the Aviation Life Support Equipment (ALSE) assisted in the overall weight considerations for flying. Consequently, the knife blade being reduced from six inches to five inches allowed it to retain some of the qualities necessary to carry out survival tasks, but small enough that it could be easily stowed on an aircrewman’s vest without causing interference for aircrews trying to carry out their duties while flying.

In particular, some questions that arise with this knife are those regarding two specific features of the knife: the saw-toothed spine and the two holes in the handguard. The serrated spine on this knife is part of the functional requirements for this knife. One of the tasks that this knife was designed to accomplish was helping pilots and aircrews egress their downed aircraft or to help first responders extract them from their downed aircraft. The serrated spine was designed to cut through the aluminum skin surrounding the airframes of Korean and Vietnam War-era aircraft. The sharpened clip point on the blade allows the pilot to punch a hole in the aluminum then use the knife spine as a hasty saw to cut through the aircraft skin during an aircraft egress situation.

Additionally, synthetic composite materials like Kevlar had not been fully integrated into aircraft construction until the late 1970s and 1980s. Thus, this knife became obsolete for its original intended use when the majority of military aircraft incorporated composite materials. However, it was still adequate for survival situations and therefore remained in the Federal Supply System.

The second question that arises concerning some of the features of this knife is the purpose of the two holes in the blade guard. As best as can be ascertained, the two holes are used as lashing points for cordage for survival tasks in the field, such as creating a hasty spear. However, there is not enough information in the literature to determine with certainty the purpose of the holes. As with many uses of military equipment, service members use considerable ingenuity in the field when employing their equipment and therefore, the use of the holes in the blade guard for cordage lashing points may have been a field expedient use of the knife rather than as an intentionally designed purpose. So, as stated earlier, the archives of Marble or the DoD may reveal conclusively if the reason for the holes in the handguard.

Further Developments of the Air Force Survival Knife

In the early 2000s, the U.S. Army published requirements to private industry for an aviation survival knife to replace the aging Air Force Survival Knife. As a result, the Ontario Knife Company developed a prototype based on the 1957 design that was first submitted by Marble. Ontario’s model became the Aircrew Survival and Egress Knife, System (ASEK) based on the published requirements by the U.S. Army. Ontario’s knife became procured by the U.S. Army and was issued a National Stock Number, NSN: 1095-01-530-0833 within the Federal Supply System. However, this was not the end of the aging Air Force Survival Knife. It is currently still in inventory with the DoD through the GSA. As a further development on the Air Force Survival Knife, the Ontario Knife Company offers a second-generation civilian version of the knife in its Special Purpose SP® series of knives. It is the SP 2, Survival Knife.

Some Concluding Thoughts

The Air Force Survival Knife has had a storied, yet obscure, history. The knife has been in continuous service with the Department of Defense for over sixty years. The iconic design features of the knife, that have characterized its look, have remained unchanged since its inception. This is a testimony to the ingenuity of the design team that developed the knife at the Marble’s company. As well, it must be remembered that this knife was designed to address a specific need for the U.S. military and was not intended to be used outside of that context. However, because of Marble’s premature manufacturing of the knife before it was awarded a government contract, the rest of the world gained the privilege to own this knife.

The Air Force Survival Knife will be around for a very long time. Even if the Ontario Knife Company discontinues their production and the DoD phases them out of their inventories, the knife will be around for commercial purchase. Surplus stores will purchase them in bulk through U.S. Government auctions, collectors will buy them at auctions, military museums will display them, and they will continue to be available for purchase on the internet. It is also suspected that knife makers will begin to find ways to improve the knife and manufacture their versions of the knife similar to what knife companies are doing with other legacy knife designs.

The journey of this iconic knife has been exciting to discover. I own one as a backup knife for my backpacking, outdoor, and emergency needs. The Air Force Survival Knife is an excellent knife. Those who do not currently own one should purchase one. It will not be long before you are won over by the versatility and practicality of the Air Force Survival Knife.

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The Original Design Proposal Submitted by Marble for a Pilot’s Survival Knife

 

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Advertisement for the Camillus Air Force Survival Knife
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The Marbles Commercial Pilot Survival Knife

 

 

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The OKC Aircrew Survival and Egress Knife (ASEK) System

 

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The OKC SP 2 Air Force Survival Knife