This is a 1940 produced S/172 code bayonet.  This is the only S code that was used in 1940.  All the other manufacturers were converting from using their name to using the 2 or 3 letter secret code.  The S codes had not been used for about 3 years and no one knows why this one manufacturer was allowed to do it.  This is a scarce bayonet but in addition is numbered by the Kreigsmarine for use by the Ostsee fleet.  The condition is not what I usually collect but I have kept it because it has to be a very rare example.