sachsr1,
A bit confusing, but you are looking at the right details.
Are the "right side" numbers associated with--placed under--the "proof marks"? Do you mean that the 5186 on the left receiver has been Xed out?
To make things a little more clear, go to the technical information part of the Forum, the link is on the opening page at
http://www.lugerforum.com/ and try to identify what numbers from your Luger are on what parts of the pistol--it makes a difference.
Is there a number, perhaps with a script letter, on the front of the frame?
Are your grips wood or plastic, and if they are plastic, could you descrive them?
Photos are always very useful in identifying a Luger, in addition we all like looking at them! If you can post pictures of yours it would help.
--Dwight