Apologies for not getting back to you much, much sooner than this but I've personally increased my family tree by one this summer and as such, time has vanished very quickly.
I don't have much information on Rudolph Gnehm except that he married my maternal great grandmother, Annie Glen, sometime in the early years of the last century and they had two daughters.
My Great Grandmother had an illegitimate child (my Grandmother) in 1901 so the marriage would have been sometime after then.