Augusta Schact who served as a witness is the daughter of Ferdinand Schacht and Emilia (presumably Fritz). They were living in Detroit in 1900 and with them is a niece, Othilia Fritz.
The following link is to a family tree on Ferdinand Schacht:http://trees.ancestry.com/tree/55684792/person/34005640568
I encourage you to contact them. They believe Emilia's maiden name is Gruenke however I
believe it is Fritz as I found the following death certificate for Clara Schacht noting that Emilia's maiden name was Fritz: http://seekingmichigan.contentdm.oclc.org/cdm/ref/collection...
Since Ferdinand and Emilia were married in Germany - perhaps you can find further clues as to their town of origin in Brandenburg District where their passenger list record from 1877 indicates
and thus giving you the origin of the Fritz family too.
Also, I have found Carl (or Charles if you will) Fritz and his wife, Henrietta, living in Lenawanee Co, MI in 1900 (census). so perhaps you will find more info there.