Hello Detlef, Your friend has done another very nice job of straightening out the damaged point on this piece too. As for why the fingerprints on the blade keep showing up after etching, I am afraid that I cannot be of any help in trying to explain why this keeps happening. Being less than graceful I unfortunately am prone to lacerating my fingertips on a regular basis when cleaning certain items in my collection and have never had this happen. Even after having the blood remain on the piece for several days it has always cleaned up with no problems and never shown up after etching.
Best,
Robert