It is commonly called the Krag-Jorgensen and was the U.S. service rifle in the Spanish-American War era. First adopted as the Model 1892, there were upgrades as the Model 1896 and Model 1898.
That one has been altered to convert it to a hunting rifle configuration, effectively reducing any collector value to near zero. Neither the peep sight nor the stock are original and it looks like there is some kind of extension on the trigger guard which would not be original. If the caliber has not been changed, it is in .30-40 Krag, a good hunting cartridge for medium size game, deer or black bear.