This is a pair of US Army Mark 17, 7x50 observation binoculars dating from around 1943-44. The Mark 17 was essentially a Mark 15 with the addition of the Mark 17 artillery adjustment reticle in the left eyepiece. There were 53,412 of them built by Westinghouse during the war using Bausch and Lomb or Optical Research Company glass elements. The stock number for this model, located on the right end cap, is 757834. This M17's coated optics place it in a time frame in both production and in development of binoculars and optics in general. The Army was looking for a means to allow their binoculars and telescopes to work earlier in the morning and further into twilight than the enemy's. They discovered that a coating of magnesium fluoride film applied under heat and vacuum allowed more light to pass and thus achieved their goals. By 1944 most American binoculars were made with coated optics. In the 1970s, the Mark 17 binocular was superseded by the Mark 19, which was developed in an attempt to create a pair of M17s with reduced size, weight, and maintenance requirements as well as increase resistance to moisture. Using modular construction and glued prisms, they were able to reduce the M17's weight by one-half.
This pair of M17s with their M44 leather case was bought from US Army surplus by my father in the 1960s for use in his work on the Tennessee River. In the 1980s he discovered that they had developed some moisture problems so we had them rebuilt and collimated by an optical repair shop that did contract work for the US Navy, the London Bridge Trading Company. Their repairman was Kent Ferguson. While he was at it, he modified them to A1 spec's (see below). My father kept them until this year (2011), when he graciously passed them to me. The Mark 17 reticle they contain is still used to this day in military glasses for artillery spotting. Pics are from before I started cleaning them up. I've included a picture comparison of the M17 and an inexpensive pair of modern, center-focus 10x50 glasses. The M17 presents a much brighter, whiter image. Due to its lower seven power magnification, it is also less fatiguing to use for any length of time and has a broader field of view.
I recently went to a gun show and saw a surplus stall where rifle slings and web gear were offered. In the middle of his stuff I found a bin of loose eyepiece rings for this pair of binoculars. When I began digging through to find a nice set for spares, the company's owner came over and helped me find the best ones. In the process of chatting I figured out that his was the company where we had these binoculars repaired. He had since closed his optical bench and just had the parts lying around so he brought them out to shows to sell. Incidentally, these binoculars are now technically M17A1s. The A1 mod consisted of removing the rubber eyeshields and eyepiece rings and replacing them with specially-shaped eyepiece rings that allowed an external set of filters to be clipped onto the binoculars. When this was done by the Army, the legend "A1" was typically scribed into the right-hand end cover next to the model name. This pair was modified to this spec. in the 1980s when they were rebuilt.
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