You should check out author Joe Nickell - he got started as a forensics investigator and then moved on to investigate historical document forgeries and real-life X-files (always with a skeptical mind of course).
pt. I. Documents -- Investigating documents -- Diary of Jack the ripper -- Novel by an American slave -- Lincoln's lost Gettysburg address -- An outlaw's scribblings -- Out of the archives -- pt. II. Photographs -- Photo sleuthing -- A second photo of Emily Dickinson -- Likenesses of Lincoln -- Assassin or look-alike -- From the album -- pt. III. Other artifacts -- Authenticating artworks and other artifacts -- Lost icon found -- Jefferson Davis's musket -- Debris from the Titanic -- Off the shelf.
Highly recommended for the historian's thought process. Clues reside in the strangest places: a turn of phrase, hairstyle, kind of stamp, anachronisms, as well as technical analysis of ink, paper, handwriting styles and more.