Tan straight E-tool carrier marked fkx 4

Textbook tan straight Entrenching tool carrier manufactured out of tan Pressstoff or Ersatzmaterial in excellent condition. The carrier is nicely marked fkx 4 which indicates production by Gustav Sudbrack, Lederwaren u. Gamaschenfabrik, Bielefeld. The carrier features additional ink markings which seem to be from the material supplier. This is the first time I have encountered this and the markings deserve further research! Simply a Perfect example which would impossible to upgrade!