P.38 soft shell holster made in 1944 by Mortiz Stecher Lederwarenfabrik KG. (jwa code). You can see on the inside that the side flap was stitched on with two different colors of thread and the top flap was stitched on with white thread.  Then they dyed all the thread black on the back so it would not show up as two colors.  This was apparently done to reinforce the high stress areas of the holster.  I have not observed this on any holster made by another maker.  Other holster collectors have reported similar stitching on their jwa4 examples. Notice the 2 small holes above the closure strap.  I have seen that on other jwa4 holsters also and assume the holes were punched as a guide for the closure strap placement.

Belt loops, top and bottom of the side flap and top of the front (where rivet is) are stitched with double black thread.

Underside of the area where the spare mag pouch is stitched on.  The double black thread is only used at the top.