As above, your best source of verifiable information is to buy an Archive letter from Colt.
This framable letter will state in what form it left the factory as in caliber, finish, barrel length, etc, any non-standard or custom features, when it was shipped, how many were in that shipment, and WHO it was shipped to.
http://www.coltsmfg.com/CustomerServ...eServices.aspx
Note that Colt may not have any records on some guns due to the big Colt fire during the Civil War.