Both the model 1907 and 1915 were being manufactured in 1915, but you probably interpreted the model number as the date of manufacture. Blue Book says in 60% condition, which would be a well-used but not abused gun, should be worth $200 retail. Untouched since it left the factory, it is listed at $525.
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If this pistol is a model 1907 in .32 caliber, then the above is more or less correct -- probably a bit low by now, late 2010. If it is a model 1907 in .380 caliber, then it is worth maybe another $100-200, depending on condition. If it is a model 1915 (grip safety, shrouded hammer, usually called "hammerless") in .32 caliber then you can add a few hundred dollars more; only about 6,500 were made. If it is a model 1915 in .380 add another few hundred dollars; only about 3,500 were made. .380 model 1915s in very good (but not pristine) condition typically sell for over $1,000; pistols looking like they just left the factory, especially if in the original box, are usually over $2,000.
The model 1907 was made 1908-1920 in .32 caliber (in about 14 versions), and 1913-1920 in .380 (in about 6 versions). The model 1915 was made 1915-1916 in .32 caliber (1 version), and 1915-1917 in .380 (1 version).
See link below for images-