It is listed in 'The Antique Bowie Knife Book' by Adams, Voyles and Moss, page 116. The ONLY Searles Bowie in the book.
If this is engraved 'S. Henderson' which was who it was presented to (Stephen Henderson), then you must be his great-great-great-grandson, who was credited as the current owner (at the time of printing.)
All I can say here is if this is the real deal, this knife is worth WELL into the six figure ranges. Congrats on such an heirloom!
Coop