Index marks(witness marks etc) are used to remove and reinstall barrels onto receivers and retain the original headspace characteristics and sight alignments. This of course, is true blue, if the parts are originally fitted to one another; otherwise you takes your chances.
With all the parts changing going on now and previously, the alignment marks may or may not indicate originality. If the marks are true, then the sights should be in alignment for shooting with a particular type of ammo. If one cranks the barrel past or before the true index mark, then the point of impact will change, just like changing ammo types.
So if the index marks are off from one another on your particular Luger, what does that mean.......I really cannot tell from here. If one pays attention to the various clearances in the breeching system, particularly around the extractor to its receiver cavity, then one might gain some insight about functionality. There are cuts in the barrel and in the receiver for receiving the extractor nose. If the extractor is off axially of its cavity(s) and scrapeing, then probably will not function as well or perhaps be long for the world.
Likewise, the tension on the extractor has to be turned for the system, such that the spring provides the movement of the nose over the case's rim. If the extractor provides the movement itself due to trash or a overly long extractor spring(excessive stackup), the extractor will eventually break in half.
Index marks are supposed to be a indication of original fitment of barrel to mechanism. As before, today's parts changing makes taking a fine look at the fit of parts rather than the index mark for shooting purposes. Index marks have the only influence on perseived value for collectors, guess they assume originality from such a visual.
of course, you all ready knew all these things...............some my remarks of course, is opinion.
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