I can't say about the man - but can definitely say he's wearing the rank insignia of a major and is carrying a Mlle. An IX or An XI Sabre pour Cavalrie Legere! Those were regulation in Napoleon's army from 1802 or 1804 to 1816 for officers and troopers of what Europeans termed light cavalry: Hussars, Chasseurs, or Lanciers. While recently reading about Second Manassas I noticed a photograph of a Confederate colonel there showing him armed with the Mlle. An XII Lourde or heavy cavalry saber. And of course, Maj. Heros von Borke of Jeb Stuart's staff carried his own Prussian model dragoon saber.
Edit: For some reason, Federal Maj. Gen. Irvin McDowell is always pictured with an Austrian cavalry saber!