Some post-1872 publications refer to this sword as the "Foot & Staff Officer's Sword" or the Staff & Line Officer's Sword. The hilt features gilded brass with a steel catch for the folding clamshell guard.
The folding clamshell allowed the sword to be worn more comfortably against the hip. The grip is wire-wrapped fish skin, likely from a ray or shark.
The blade is diamond-shaped in cross-section and bears the markings of a post-1872 issue sword. The scabbard is steel, with a nice speckled plumb brown patina and brass drag and ring furniture.
The sword and scabbard are highly decorated. The pommel displays an eagle and Federal Shield, with a blank tablet (possibly for optional initials) on the reverse. The front clamshell shows the American eagle with arrows and olive branch, surmounted by the Federal Shield in front of a stand of colors. The back clamshell features the Federal Shield in front of a trophy of arms, oak, and laurel branches.
The blade's outward side is etched with floral sprays, military trophies, and U. The reverse side replaces the U. With an American Eagle and Federal Shield. The guard and scabbard ring furniture also have floral sprays. Your specific sword is attributed to William Reed & Sons of Boston, Massachusetts.