I saw this rifle when I visited Reed Knight’s Institute of Military Technology a while back, but didn’t have a chance to examine it. Well, he took it off the wall for a video segment with Jerry Miculek, and it’s definitely worth watching:
As I recall from asking about it at the time, there is no definitive evidence of exactly who made this conversion or when it was done, although the quality of the work is excellent. Springfield Armory has documented the attempts at developing a semiauto 1903 conversion, although they may not have included designs that failed to gain enough official notice (you can read their history here, in PDF form). Of the three designs that were recorded, this could theoretically be either a Young or a Hammond (same Grant Hammond who designed an unsuccessful challenger to the M1911). The third, the Smith-Condit, is definitely not this rifle (I will be writing up an article on that design next week). I have been unable to find any description, drawing, or photo of the Young system, so I can’t comment on it. The Hammond design was patented (download the patent here), but it is difficult to say if that matches the rifle in Knight’s collection, because details often changed between patent drawing and working model, and because of the lack of mechanical detail shown in the video.
Around the turn of the century there was a tremendous amount of interest by many governments in converting bolt action rifles into semiautomatics as a way to get the new technology without having to scrap all their existing rifles and buy new ones (a similar interest existed 50 years or so earlier, to convert percussion guns to use metallic cartridges, and before that to convert flintlocks to percussion locks). Most of the attempts had about as much practicality as this one, but most did so with a rather lower standard of workmanship.
To the best of my knowledge none of these types of conversions were ever accepted and mass-produced by any government or military force as an infantry rifle (though the Australians did make a significant number of Charltons as light machine guns). Here are a few other examples of the idea that I have covered previously: