looking at this again, I suspect that was stored for some time with a heavy object on top or squeeze in some way that left this imprint.
Note that although we collect these artifacts and deplore those who neglect them, some people have little respect for "Nazi junk". This way more true years ago.
In 1973-74 I lived in Indianapolis and my neighbor used an SA dagger as a yard knife. He ground off the ends of the upper crossguard to make it easy to use and when it got dull, he would sharpen it up on a grinding wheel.
Dave
