UBB.threads Forums Edged Weapons SS Dagger Forum Transitional SS Eickhorn:

I might add that ANY raised tang mark on an SS/SA/NSKK/NPEA dagger is IMO a VERY strong indication of an original blade. I can't recall EVER seeing a fake with this feature in over 50 years of looking. Also, fake blades are almost always narrower where they meet the cross guard and a trained eye can see this right away.
Some originals of course don't have these marks. Also-the blade could be altered in some way. But--raised tang marks are a feature that I always like to see.