Diam. 33 mm token repurposed as a dog tag (wear, light surface scratches). Punched twice. Obverse ID reads: "M. Mc'Keen / Sanborn / Iowa" surrounded by 12 stars at perimeter. Reverse marked "Bank Token / One Penny" with the year beginning "18" partly obliterated. 

Possibly Miller McKeen who enlisted on 6 October 1863 as a private and was mustered in the same day into Co. B of the 4th Iowa Cavalry. He mustered out on 8 August 1865 in Atlanta, GA.