To be brutally honest Solingen Knives are pretty mediocre quality wise, ....useless in the field. The steel is of low quality, never keeps a sharp edge & liable to break under shock. As it is a treasured possession my advice to you would be, sharpen it by all means but to keep it as a collectors piece & not as a user.
Sorry, but that's utter nonsense!
Do you have a working knowledge of ALL the Solingen makers to make such a sweeping generalisation?
I've owned and handled some blades with Sheffield stamped on them that could best be described as Monkey Metal.. Doesn't mean that every blade from that area is the same!