KU luger questions

[Robgunbuilder]

I have a opportunity to purchase a Ku BYF 41 luger rig but have some reservations. The gun has the same markings as the one described above, but no matching serial number on the barrel or back of the toggle. Other parts like the sideplate, trigger etc are numbered correctly. I was told that many Ku lugers have these discrepancies. Is this correct?-Rob