Horace Warner was an officer under the command of Hiram Berdan as a member of his elite Sharp Shooters squad.  He is quoted on page 44 of the book "US Sharpshooters Berdan's Civil War Elite" by Roy Marcot extolling the virtues of the American target rifle ie the heavy barreled single shot percussion target rifles of the era used for sniping.. He is pictured on page 124, listed as Ordnance Sergeant of Company C Pennsylvania 2nd US appointed regimental quartermaster in the Sharp Shooter Brigade.  The letter from Major James Miller requests that "Lt Horace Warner, late 2nd US Sharp Shooters aligned to the regiment per special order military war dept..." in which he is being reassigned.  Nice condition and interesting in that it pertains to one of the officers in the Berdan Brigade.  Included is a copy of the Military Images magazine from July August 1979 that pictures the four Warner brothers in service together.  If you have a nice Berdan's sniper rifle or a heavy barrel target, this would make a nice display.