It's a lot like the development of the AK-47. How much of it was Mikhail Kalashnikov's input versus that of the other designers he worked with is unknown. It is known that Mikhail didn't come up with the entire thing from buttplate to muzzle. John Browning created the first prototypes on his own, but the development of the M1905, M1907, M1909, M1910 and finally M1911 was accomplished using a lot of input from the Army Ordnance board, Springfield Armory and Colt engineers. Exactly how much and what parts of it we will never know.