Additional observations:
- He is a dandy
- Does not look like a frockcoat, but a short jacket
- You can see both double trouser stripes all the way to his waist
- Has the regulation Civil War (1861) seven button front for Colonel and Major
- Unusual button pattern
I was thinking possibly post war Major, but no longer think so, pension request records from wife could possibly shed light.
I was looking to see if SK Zook had a son who served.