The picture Doubs posted illustrates the final inspection and proof marks.
Pictured below is a detail study of a 1914 Erfurt LP-08. I've pointed out the small inspector's stamps "peppered" over the pistol's surface, demonstrating inspection of each of the small parts including the ejector and grip screws (bottom two).
Instead of the Crown/U, the 1906 could have had a combination of Crown/B, Crown/U, Crown/G proofs, pictured here.
You have already seen the Crown/N to notice the difference; late Mauser commercial Lugers have a Crown/U proof.
--Dwight