We could try to use his clothing to pinpoint a time period, but that can be a little more difficult with men's clothing. The back of a photograph may give us some clues.
The blue stamp is a revenue stamp required by the the United States government to raise money to fund the Civil War. The tax began on 1 August 1864 and was ended on 1 August 1866. So this photograph could have been taken anytime between 17 June 1865 and 1 August 1866. In addition, the back of the photo shows the photographers rather intricate engraving which says:
"Photographed by HOPE
Successor to W. H. Kimball
So far my attempts to find "HOPE" in city directories in ancestry.com have been unsuccessful. Finding out when a photographer was in business at a certain location could possibly narrow down the date.
Still, we do know that this photograph shows W. Hunter within about a year after his release. He looks rather thin but well-dressed.
Doing the photo detective work is rather fun. I got some good ideas how to find clues from Maureen Taylor's Family Photo Detective (Family Tree Books: Cincinnati, Ohio, 2013).