10 C. postal stamp ultramarine with overprint "fortress Lorient" as horizontal gutter pair with likewise overprinted empty space - variety "stamp and empty space with inverted overprint", printing machine number "3" on the gutter - in existing form probably the only one exists, slight defects like slightly thin perforation respectively left stamp with wood inclusion and brown spot, issued only 650 stamps - gutter pairs are only approximate 65 possible, but only a small part is as those remained well preserved - extremely rare, photo expertize autumn VP (2017), Michel - .