Very nice original GI customized P38 holster : for quick draw, the GI cut a part of the inside flap; he also add a leather thigh strap and some extra leather straps on the belt loops.
Markings are found on the back : jln (Deutsche Lederwerkstatten G.m.b.H. in Pirmasens) and 1943 dated with the WaA : E/WaA145. And the P38 logo, of course.
Many other customized holsters are detailed in the book WW2 German Military Holsters !