Original U.S. WWII M13A1 6x30 Binoculars with M17 Leather Case

Item Description

Original Item: Only One Available. The M13 and M13A1 binoculars were issued to all branches of the U.S. military during WW2. 43,378 were made at an original price of $72/ea. They are marked on the left Binocular M13 6 x 3.

This example is offered in very good condition with clear optics and an original CASE, CARRYING, M17 with shoulder strap. These are often found without a case making this pair a hard to find set. The focus diopters both function, though the left side is stiff, due to the grease drying out in the threads. The right diopter move easily.

The following is an excerpt from All about Binoculars, by Albert G. Ingalls. Scientific American, August, 1944

The binocular M3 is a superlative instrument However, after a quantity of the M3 binoculars were issued and in use many difficulties due to the nature of military operations of World  War II were reported. As a result of these reports, a concentrated study of the  most minute details of Binocular M3 was conducted, which  eventually resulted in the development of Binocular M13. The first problem to be considered in the development of the  M13 from the basic M3 was that of waterproofing the instrument  to withstand submersion. This was accomplished by redesigning  the cover plates to provide for the use of a synthetic rubber gasket and a greater number of fastening screws. In addition, a  new military wax, capable of withstanding extreme high and low  temperatures, for sealing the objective lens and objective assembly was developed by the Ordnance Laboratory. This  compound, Specification FXS, replaces Navy Black Sealing  Compound No. 3A. It resists cracking at -50 degrees F. and has a  melting point of 210 degrees F., as against 150 degrees F. for  No. 3A compound. The formula includes a fungicide to repel molds  and insects. Shock and vibration tests revealed that severe shock caused  shifting of the original prism mounting, affecting the optical  alinement of the instrument. Experimentation with methods of  mounting prisms resulted in the use of a dental cement. This  cement is a blend of cupric oxide powder, phosphoric acid, and  zinc chloride in solution. The ingredients are mixed in the  ratio of three parts of powder to one part of liquid. Additional  tests proved that prisms mounted with this agent were locked  firmly against all shock remained free of strain, and could be  removed readily for cleaning. Another very serious problem, applicable to all telescopes,  was the formation of moisture on the optical elements within the  finished instrument. In any binocular, moisture may eventually  enter and condense on the optics, because no instrument with an  adjustable threaded eyepiece movement can be sealed perfectly.  Such formation is most objectionable on tee graduated reticle,  upon which the most trifling speck is visible and distracts the  user. A plane high in the sky first appears as a tiny pinpoint  which looms very like a fleck of dust under magnification of the  binocular eyepiece. Experience gained in packaging complicated items for export,  using dehydrating agents, was utilized in solving this problem. A special cartridge, shown in the small illustration, containing  a small amount of silica gel, was placed within the body of each  binocular. The instruments so treated were tested by subjection  to most adverse conditions of humidity and rapid changes in  temperature, which proved that the desiccant eliminated  formation of moisture on the optics over an extended period of  time.    A means of making the binocular more usable under conditions  of fading light was undertaken. American binoculars effective an hour later in the evening than those of the enemy would be of  great advantage to American soldiers. Therefore, a development  of the optical industry-coating optical surfaces with a  magnesium fluoride film to reduce loss of light by reflection- had been under study by the Army and Navy for some time. By  exerting the full power of research of the Army, Navy, and  associated commercial facilities toward perfection of magnesium  fluoride and other coating techniques, coatings were produced to  withstand cleaning and all field conditions. The magnesium  fluoride coating is applied to the optical surfaces at high  temperature under a high vacuum, the fluoride becoming a part of  the glass surface. This coating reduces light reflection and  permits a greater amount of light to pass through the optical  system, enabling the use of the binocular at dusk, when light is  fading. After the time and money spent in producing a fine binocular, an improvement in the export method was incorporated as further insurance that the binocular will reach the ultimate user in  factory-new condition. The binocular is placed in its special  leather carrying case and sealed, together with five ounces of  silica gel, in a moisture-vaporproof bag and cushioned in a  corrugated carton. Twenty-four such cartons are then packed in a  steel-strapped wooden box having a submersion-proof bag lining. This new M13 binocular is now in mass production. Thousands of  them are being shipped every month to American fighting men overseas to aid them in seeing the enemy before the enemy sees them. Of course, the Ordnance Department is never satisfied with the degree of perfection of the fighting equipment of our Army. Even now additional improvements to assure that the American  binocular is the best the world are in progress.

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