Colt 45 revolver

A friend of mine's dad recently passed away. My friend is not interested in guns. He found an old Colt revolver in a shoe box in his dad's closet. He gave me the gun.
On the barrel it is marked "Colt DA 45". The serial # is XX176. In the box were some old 45 LC bullets. The weapon resembles the Colt Double Action New Army, Model 1905, but the front sight is not a round blade, but fin shape like a shark's top dorsil. Is this a civilian verison of the New Army? Could this relvolver shoot 45 LC?