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U.S. Army Lensatic Compass
The Lensatic Compass, the most common military instrument for measuring direction, was first during World War II, an evolution of the pre-war Compass, Prismatic M-1938. At that time, the U.S. Army Corps of Engineers was responsible for compass procurement so most models had "Corps of Engineers" stamped on the case. During the war, these compasses were manufactured by Superior Magneto Corp. (Long Island City, NY) and W. & L.E. Gurley (Troy, N.Y), with the "Corps of Engineers/US Army" markings. The Olive-Drab page "U.S. Military Gear: WW II Compass" has photos of these early models.
U.S. Military Lensatic Compass
The Corps of Engineers Lensatic Compass was the most common style in use during World War II, particularly later in the war as the other models were phased out. The compass was issued to officers, squad leaders and specialist troops only, although most troops received training in compass use for land navigation. The World War II Lensatic Compass remained in use until replaced after 1950 with the modern lensatic compass, called "Compass, Magnetic, M-1950" the design that continues in use.
Unfortunately this compass design was not moisture-proof or waterproof, leading to problems in the field in Vietnam. Like all magnetic compasses, the needle aligns itself with the local magnetic field and is attracted by nearby objects containing iron or electric circuits. If it is tilted only a few degrees off level, significant azimuth errors are introduced. The readings by two users can differ significantly and errors in transcribing the reading are easy to make.
U.S. Military Lensatic Compass Since the M-1950
With the Compass, Magnetic M1950 the Lensatic Compass design changed, although only in details. The cylindrical body was extended to a rectangular base that includes a map scale and straight-edge. Other small improvements were made to the earlier wartime Lensatic Compass. The photo to the left shows one of these compasses, produced in November 1951. Note that it is stamped U.S. but does not have any identification of the model number of the compass itself and that the Corps of Engineers is no longer responsible for procurement.
The image immediately below from Army Field Manual FM 21-26 Map Reading (March 1956) illustrates the compass and its parts:
The Lensatic Compass was always associated with a case or pouch, although the case was sometimes issued with the compass and was sometimes a separate item of issue. The Olive-Drab.com page on Compass Cases details the history.
Manufacturing History of the Compass, Magnetic
From the 1950's into the 21st Century, the Lensatic Compass was procured in large numbers for the U.S. military ground forces, and other related uses. During that period a number of manufacturers were contracted to build the units and small variations in design were made. This chart summarizes some of the particulars of that history.
Compass NSN 6605-00-151-5337 is deemed "operationally unserviceable" and compass 6605-00-846-7618 was condemned in 1978 for safety reasons and was not authorized for use thereafter. Both of these should have been replaced in miliary inventory with NSN 6605-01-196-6971.
Where to Buy a U.S. Military Lensatic Compass
If you are looking for a vintage U.S. military Lensatic Compass, use the eBay listings on this page or by searching eBay on a regular basis. Others will be available from time to time from militaria dealers.
Since September 1992, the lensatic compass has been produced with tritium luminous markings for the U.S. Government by Cammenga, under NSN 6605-01-196-6971. The Cammenga model can be purchased new from Amazon.com at this link.
There are many imitations or copies of this popular compass model so beware of cheap imitations that are similar to but not the same as the units produced for the U.S. Government.
Find More Information on the Internet
There are many fine websites that have additional information on this topic, too many to list here and too many to keep up with as they come and go. Use this Google web search form to get an up to date report of what's out there.
For good results, try entering this: lensatic compass army or military. Then click the Search button.