Probably the best way to tell is by serial number. They will fall between 467,000 and 469,000. On the right side of barrel (at breech) MADE IN FRANCE. Various markings on bottom of barrel at breech. Rampant colt insignia and Colt logo, both on a circular disk, set into bottom of pistol grip. If you have the book of Colt Firearms it's on page 520.