This is a semi automatic rifle designed by John Pedersen, Wyoming's most prolific inventor. This rifle competed with others early on for the replacement for the M1903 Springfield. That ultimately went to John Garand's design.
More patents are held by Pedersen than any other Wyomingite. Born in Grand Island Nebraska, the family moved to Jackson Hole when he was a child and he designed most of his designs from there. Pedersen continued to use the family ranch as his home base for most of his life, although he traveled extensively and did live in other localities from time to time. At the time of his death he was living in Massachusetts, near Springfield Armory, and perhaps because he was working for the United States government.
His most famous design, although not his most successful one by any means in terms of manufacture and use, was the Pedersen Device, a device which allowed for the 1903 Springfield to host what was basically a semi automatic action. Manufactured in numbers during World War One, they were never actually issued and were discarded after the war. His design for a pump action shotgun, however, lives on today ironically as the Browning BPS. His Model 51 pistol was manufactured commercially by Remington and was recommended for purchase by the Navy prior to World War One, although it was not officially adopted. The cartridge design he created following World War One for military trials, the .276 Pedersen, turned out to be far ahead of its time, although the wise intervention of Douglas MacArthur, given budget constrains during the Depression, kept it from being adopted.
While a very successful arms designer, with many important patents to his name, a great deal of his personal story is lost. He was married and had two children, one of whom was a Marine Corps lieutenant during the Korean War who purchased the famous racehorse Reckless for use in hauling ammunition. His wife was a published author who wrote on widely varying topics. The divorced at some point, but it is not known when. He later remarried late in life to a woman 32 year his junior.
Pedersen would be famous today but for the fact that he was a contemporary of John Browning, the most famous of all American firearms designers. Browning, for his part, called Pedersen the "greatest firearms designer in the world."