Walt,
in my best of humble opinions...if it doesn't say that its a Kreighoff, then it isn't a Kreighoff. From reading this forum for a few years, even if it says its a Kreighoff, it still MIGHT NOT be a Kreighoff. I would have to know who the "very knowledgeable Luger collector", that you mentioned, is before I would say anything about him. Some of those people ain't as knowlegable or as ethical as one would expect.
Another humble opinion...a refurbished Luger is not be a Kreighoff, no matter what internal or external minor proof markings are on it. It is a restored Luger. (Boy, am I going to catch the dickens on that one
)
Big 'humble' Norm