This is a rare P.38 hard shell holster.  It was made by Ehrhardt & Kirsten, Koffer & Lederwarenfabrik, Tauscha-Leipzig who used the code of E. K. St.  This is not the usual letter maker code that was assigned by the Third Reich starting in 1940 or so.  There is no explanation as to why they are an exception to the code rule.  This maker also made P.08 holsters.  This is only the third P.38 holster by this maker I have seen.