I would opine that the notion that it is possible to authenticate a Luger, particularly one of the Navy variants on the basis of photographs alone</u> bears some serious scrutiny, regardless of the experience level of the examiner.
The quality of the boosting I have encountered over the past several years was sufficiently high such that detailed disassembly and examination under magnification was required to positively verify originality. In fact, I do this as a routine procedure with each new acquisition. In several cases I have encountered, I sought second opinions from others, not wishing to trust my eyes exclusively as final authority.
This is not to say that some fakery cannot be spotted via photographic examination, but such fakery must be generally pretty crude, in my experience.
My two cents.