Can you answer this "Riddle"?

Unidentified Riddle Family Photo

A Riddle within a Riddle 

Can you help identify this photo? 

Bonney Valencia of Troy, Ohio sent this photo to the Rockcastle County Kentucky Historical Society with the following query. With her permission I am posting her query and the above photo.  

"Can anyone identify any of the people in this photo, or identify the organization, or time period? The photo was among a group from the Riddle family of Rockcastle County. I'm hoping one of the men may be Robert Riddle, 1810-1890, who lived in the Brindle Ridge area and served with the 4th Regiment Kentucky Mounted Infantry Company B of the Union Army."

If you can give any information regarding the photo, please contact me.