I purchased the subject undated studio photo of a middle-aged couple taken by J. G. Mangold, No. 56-1/2 Main St., Moline, IL. It is identified on the back of the mount:
"Mr. & Mrs. Gluising"
I believe that whoever labeled the photo misspelled the surname, which I can't find on ancestry.com. The most likely candidates for these individuals are saloon keeper Diedrich Gluesing, born about 1832 in Germany, died 1889 in Rock Island Co., IL, and his wife, Margurete First, born 27 Jan 1834 in Germany, died 15 Apr 1930 in Moline, Rock Island Co., IL, the daughter of Hans Henry First and Elizabeth Roberts (her death is listed in "Illinois, Deaths and Stillbirths Index, 1916-1947").The couple had six children (all born in IL), including: Frank H. Gluesing, born Jan 1861 (or 30 Jun 1864), died 28 Nov 1924; Lizzie Gluesing, born about 1862; Annie Gluesing, born about 1865; John W. Gluesing, born Sept 1866; and Mary Gluesing, born Mar 1870.