John, depends on if military or commerical. Commerical are "hidden", and not obvious, unlike the military markings.
I am sure I will forget something, and believe that WW1, Weimar and Nazi era are marked the same for military, but someone correct me if I am wrong.
Frame, barrel (this depends on year manufactured, not all have it), breechblock, firing pin, extractor, take down lever, hold open, sideplate, magazine catch, trigger, sear bar, safety bar...
Grips, but not always, depends on year...
Look here:
http://www.lugerforum.com/lugermarki...tmarkings.html