On April 9 – 12, 1865, Archibald Van Orden wore this ribbon on his uniform, signifying his position in an honor guard accompanying General Grant at ceremonies of surrender on the grounds of Appomattox Court House, Virginia.
Worn by Archibald Van Orden, 16th NY Cavalry, at Appomattox, VA.
On April 9, General Lee surrendered his Army of Northern Virginia. On April 10, the CSA cavalry surrendered. On April 11, the CSA artillery surrendered. On April 12, the CSA infantry surrendered. At this final occasion, Joshua Chamberlain ordered the US Army to salute the CS Army with a command of “Order Arms; Carry!” The surrendering forces returned this action of mercy with their own Marching Salute. By honor saluting honor, the two armies began the healing of repatriation.
The painting below depicts cavalry to cavalry surrender on April 10, 1865:
CSA Cavalry surrenders to USA Cavalry.
The Assassin's Assassin 
How wonderful this cherished mementos managed to survive from generation to generation.