For those that have Brophy's book, there is documentation and pictures of the experimental Model 1901 Rifles. I was fortunate enough to have recently acquired two Model 1901 Receivers from a very old collection. I thought I would post this to share with others interested in the development of the Model 1903. The two receivers I have are in the white and apparently never assembled. They were probably disposed of many years ago by the Armory and made their way into an old collection in PA. They are the second type with the closed rear receiver bridge. The key features of the 1901 receiver that are different from the 1903 are the smooth rear bridge with no reinforcing hump, the cutout on the left side for the thumb when using the stripper clip and the extension of the front protrusion for the safety about 1/2 inch longer than in the 1903 receiver.