There are no dates on the stone, but I doubt that Marion Harris, buried beneath a Civil War-style gravestone, was a Vietnam vet.
57 OHIO INF.
According to American Civil War Soldiers [database on-line via Ancestry.com] compiled by Historical Data Systems, Marion Harris enlisted on September 23, 1861 at the age of 17. He received a disability discharge on April 29, 1862 at Camp Dennison, Ohio.
Certainly not a Vietnam vet.
Canaan Cemetery, Marion County, Ohio