Available serial number records show this Colt being built between 1863-1864.
Over 140 Union Cavalry Regiments are known to've carried the Colt 1860 Army during part, if not all of their service - it was issued more than all of the other revolvers combined - with 84% being shown to be on-hand at with the Union Cavalry Regiments at Gettysburg.
I'm away from my primary library.
Your only recourse is to follow whatever oral history is available, while you look up the locale where the 7th Virginia Cavalry was engaged after mid-1864 - allowing for shipment to be made to the Quartermaster Department, and then issued out to the Regiments needing them.
Good Luck!
Vaya,
Scouts Out!