R.L. Wilson has some excellent firearms books, including "Steel Canvas", "Silk and Steel" (about women and firearms), Winchesters, Colts, etc. I just got his book "The Peacemakers, Arms and Adventure in the American West" from Edward R. Hamilton, Bookseller, for $17.95. ISBN: 0-7858-1892-8. In this book he has photos of Kit Carson and Jim Bridger Hawkens plus others, including a .70 caliber with tang ladder peep sight that was in Theodore Roosevelt's collection, originally owned by Kit Carson, and four pistols. He writes "A specialty of the author's profession is the authentication of collector's firearms, particularly American antiques." And, "As with Indian arms, collectors of mountain man pieces need to exercise particular caution to avoid acquiring cleverly altered originals or patinated replicas."
He pictures a Hawken I've not seen before, and his caption is "TOP, by Samuel Hawken, and so signed; full-stock, and converted from flintlock to percussion. One of earliest Hawken Plains-style rifles known."
The rifle has a steel pineapple patch box, a silver crescent forward of that, brass tacks in the wrist, silver key escutcheons, and the rear sight has been moved back about six inches. There is no snail but a drum screwed into the side of the barrel. Well- it was a flintlock.