Joseph Schiefer - Germany mid-1800s to early 1900s (?)

My grandmother's father is Joseph Schiefer.
My grandmother's wedding certificate lists her parent's names and that they are alive and resident in Cologne and that Cologne is my grandmother place of birth.
My living relatives believe that Joseph was granted a taxi license in Cologne when he was discharged from the German army at the end of the 1870 war (his participation in the War of 1870 is the basis for my approximation of his birth in circa 1850).
My understanding was that Joseph lost a leg in that war, whether that info is of any use i don't know :)

So a German man who fought in the Franco-Prussian war and was alive in 1931, but possibly with only one leg, shouldn't be that hard to find him!