Henry Deringer was well-known for his pocket pistols to the point that many eventually carried the generic (and misspelled) name of "derringer" (note double "R"). In 1842, he contracted with the United States Navy to deliver its first percussion cap-based pistol featuring a rifled barrel. The percussion system improved reliability over the long-running flintlock types while rifling improved range and stability of the outgoing bullet. The sidearm in question became the "Henry Derringer Model 1842 Navy" which saw production span from 1842 to 1847 with totals ranging from 200 to 1,200 units (sources vary). The pistols were stamped with "US Derringer Philadelphia" branding along the lock plate.
Outwardly, the pistols were of a typical design for the time. The body was of a wood (walnut) with the lock plate along the right hand side. Brass was used at the trigger ring, butt cap and the single barrel band. The barrel was set upon the wooden body in the usual way, the brass band used for structural stability. The hammer was offset to the right sight and set to fall on a nipple to which a percussion cap would have been seated. The barrel was short and stout, chambered for .54 ball ammunition. The ammunition and powder charge would be inserted through the muzzle manually and the included metal ramrod was used to push the contents closer to the action.