The 1891 picture is not a "Civil War" uniform but a Veterans Fraternal Order Membership "uniform". The larger medal/badge with the Eagle on top, Ribbon middle an Five Pointed Star at bottom is the Grand Army of the Republic Membership Badge, (GAR).
http://bentley.umich.edu/research/genealogy/cw/fraternal.phpThe GAR are (Federal) Union Army, Navy and Marines Veterans. So since he was a member of GAR, then the second picture of him in a Union Army Uniform...
Where did he live in 1891, see if local GAR is still active tofay as a Sons Of GAR or if there is an archive of local membership files...State Library?
Have you found him in the 1890 Special Veterans Schedule census? It was not destroyed in the fire that affected the 1890 Federal Census. It will have his unit and time in service. It can help pinpoint him in the National Parks Civil War Soldiers and Sailors website, if he has a common name.