Welcome Vincent to the forum!
Your best bet is right in front of you, this forum
I could say, watch for this and this, and then it ALL depends on what year, what manufacturer you have in your hands.
So, the best thing I can say is, ensure it is all matching and it is all original, i.e. not reblued.
Find out, and take lots of digital pictures of each luger. Lugers are just like 1911A1's, they were rearsenaled at times, they had parts swapped etc., but in the luger world, more original equals better collectability.
Get the basic info of the guns, then post back here...
Ed