I checked the:

• Missouri Archives Civil War Database
• Kansas Historical Society Civil War Rosters
• Civil War Data Base (subscription-on-line)
• Ancestry.com's Pension index.

I found nothing except on the pension index:

Andrew J. Obenchain Appl #367199(?) 10 Apr 1880
Nancy N. Obenchain Appl 543451 IA 10 Mar(?) 1893
Wagon Master QM Dept US Vols

He may well have been a civilian employee of the Quartermaster's Dept., US Army. I was unable to find any enlistment.

I did check under all names starting with Oben and Aben. Lots of variations in spelling. I did not check any Obben/Abben, etc.

Sorry for negative response.

Mahlon Erickson