Robert, In the Summer 2007 GCAicon Journal the "Featured Rifle" article, " The Mysterious 6100202", by Bob Seijasicon, will give you some insight into these 6.1 receivers/rifles. At the time of the 2007 article it is stated that only 4 rifles and one (1) bare receiver had been found, and that "Army records" show that two others had been destroyed ". Last time I asked if any others had turned up was in Feb. of 2010 and Bob Seijas replied that he had nothing later than the 2007 article. It would be interesting to know if any others have turned up and if the rifle you posted was one of the known rifles in 2007.