You see many, many guns with non-matching numbers.
When you say 3 different sets of numbers, can you explain more?
I mean, you should have the number on the frame (front by the trigger guard), then you should have it as the last two of the serial number on many assorted parts.
Then if you meant what you said, and its not matching, well, it is considered a shooter or representative piece for a collection, meaning, you have a real Luger and others don't,

Depends on how much you paid? Anything less than $550 is reasonable now-a-days,
Ed