Your serial # 12151 - found serial # 12150, issued to Company C, 10th Michigan Volunteer Cavalry on December 11, 1864;
Your serial # 7729 - nothing close - maybe a state purchase and serial # not listed even close to your # 7729 HOWEVER, serial # 7728 a Spencer Carbine was issued to Company E, 11th Ohio Volunteer Cavalry on August 21, 1863.
RimFire DOUBLE CHECK your serial #s - match under the forearm?
Two Spencer Rifles?
?
Two Flints