Yes the blades have been replaced all, I have read: Friodur J.A. Henckels
It comes with the 1900 logo:http://de.wikipedia.org/wiki/Zwilling_J._A._Henckels
1951: Introduction of the ice-hardened steel blades under the name Friodur
Theoderich and Zilverik both mention a reference to books, is it by any chance possible to see these pictures?
Even though I have 6 of these knifes and are really bad to read all, maybe I can give it a try to compare?
All thanks for all info/help/suggestions so far