The more lugers you look at the more differences you will see in that "mark".
Some are one sided, some are very thin, maybe there are a few that are just right and don't have a mark, some are worn considerably-perhaps from hot ammo, lots of use, or a weak mainspring.
The mark is entirely "normal" and varies with respect to appearance/wear.
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03man(Don Voigt); Luger student and collector.
Looking for DWM side plate: 69 ; Dreyse 1907 pistol K.S. Gendarmerie
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