Coincidentally, I am currently in the process of tracking down a person also called Jurgen Hess who has an eerily similar background to the one you are describing! He was some kind of sea merchant who visited my granny up off the north east coast of Scotland. He too would roughly be in his 70s now, she would have met him around 1960...
I would be curious to know if you had any luck with your search? And whether you have any further information about him or where maybe he lives now? I see your post was done three years ago - but hope to hear from you anyway!