I purchased the subject undated studio photo of six young men and six young women taken by Joseph M. Harkless, Valparaiso, IN.Although not labeled as such, I believe this photo depicts a student class at Northern Indiana Normal School (the Indiana Historical Society has it its collection other photos of students at this school taken by the same photographer).
A man and woman standing side-by-side in the back row are identified as:
"3. W. F. Dunkleberger 4. Laura Dunkleberger"
Searching ancestry.com, the only likely candidates I found for these individuals was William F. Dunkleberger, born 26 Feb 1870 in Warsaw, IN, died 26 Mar 1939 in Warsaw, IN, who on 10 Oct 1892 married Laura L. Shock, born 15 Sep 1874 in Warsaw, IN, died 26 Apr 1951 in Warsaw, IN.I found this family listed in the 1900 Census data for Rose, Payne Co., OK; the 1910 and 1920 Census data for Warsaw, Kosciusko Co., IN; and the 1930 Census data for Wayne Township, Kosciusko Co., IN.In 1900 William was a farmer, and in 1910-30 he was a house/buildings carpenter.The couple had two children--Laurence J., born Apr 1899 in OK, and Pearl, born about 1902 in IN.