John's CDV is signed in period ink, and although the imprint is partially damaged, it was taken at J. Van Stavoren's Gem Gallery in Columbia Tennessee, C. Several hits on Google searching for John S.
Photo of him and a personal account of his involvement in the Battle of Stone's River, Tennessee. CDVs are about 4" x 2.5" with some wear and soiling, as shown. The item "Signed ID'd Civil War Soldier SGT MAJ JS Dollinger 1st Ohio Cavalry / Tennessee" is in sale since Saturday, April 25, 2020. This item is in the category "Collectibles\Photographic Images\Vintage & Antique (Pre-1940)\CDVs".
The seller is "jack_mord" and is located in Woodinville, Washington. This item can be shipped worldwide.