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.
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.
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.
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.
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.
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.
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).
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: