Brian ,
Colt pistols were popular before the war and during the war and saw a lot of use . They were carried by soldiers on both side . First you need to know what Model you have and then the serial number will tell you what year it was made in . The 2 most popular models were the 1851 Colt Navy in 36 caliber ( hex barrel ) and the 1860 Army Colt in 44 caliber ( round barrel ).Go to Google and look up these two models to see if they look like yours . If not then look up Colt Percussion Revolvers till you find which you have . Then post the serial and model number and I or others can let you know the year it was made .

Jim