Solingen Rostfrei Ivory Handle knife set

There are 4 knives in the set, each with a different carving on the handle. There is a tag in the box that says genuine ivory, but does not state the source of the ivory. I found them in my father's belongings and am unsure of the age. They are in the original box with the original tags. 

I have searched the internet and can't find anything similar. Thanks for your help.