The Colt M1907 is an American prototype pistol. The pistol is well known as being the winner of the 1907 US Pistol & Revolver Trials.
A significant developmental iteration of the Colt M1900, the M1907 was submitted to the 1907 US Pistol & Revolver Trials, and was sent to various cavalries and squads for testing in 1908; 207 M1907s were made, with 200 for testing and 7 "overflow" pistols which were backups in case one of the 200 mucked up. Unfortunately, the M1907s were plagued with lots of reliability problems such as breakages of the sear and failures to eject, along with prejudice by various testers of the weapon who were already very used to using revolvers, to which Colt responded to each of those complaints.
Other than that, Colt kept coercing the testing committees that the pistols worked fine; this did not work out very well due to the obvious reliability faults and bias towards revolvers by the various testing committees. In 1909, Colt decided to take back all 200 pistols to the Springfield Armory for refinements and send them back for testing in batches.
One of the refinements made to this "batch" of pistols was an enlarged ejection port; this practically eliminated problems relating to ejection failures on this weapon. After refinements, these pistols were later sent back to the testing committee, which after some more testing, were starting to warm up to using a semi-automatic pistol as an infantry weapon as opposed to a revolver, though there was inevitably still some prejudice against these pistols.
The M1907 was one of two finalists in the 1907 trials, the other being the Savage Model 1907; while it was a close fight, the M1907 eventually won out and would later be redeveloped and redesigned into the M1911 pistol. After the trials, 185 of the original 200 M1907s were sent back to Springfield Armory as these were never meant to be actual production guns to be used in cavalries; presumably, the other 15 were cannibalized for parts or rendered inoperable and discarded.
After being sent back, the pistols were considered to be refurbished and refitted, but the Springfield Armory later on decided that it was not worth the trouble to do so, and as such, ended up selling all 185 pistols as a single batch at an auction; the winner was the Bannerman Company of New York, a famous surplus firearms dealer at the time, with a bid of $1644.44 (approximately $42,573.32 in 2017 USD), with Bannerman later selling these pistols; the original cost of these pistols was $25 and an additional $5 to refurbish them. Of the original 200, 5 pistols were used as prizes for marksmanship championships and were engraved with the shooter's name; at least one of those 5 is known to exist to day.
The Colt M1907 was essentially a M1905 with some refinements. An easy way to differentiate a Colt M1905 from a M1907 is the addition of a grip safety on the M1907. The M1907 did have a loaded chamber indicator, something the M1905 did not have.