60 pfennigs on 40 cent airmail (I), gray red / turquoise gray with dark blue engraved printing overprint, GC-paper a, overprint in type I, with overprint variety Ia: "gap between 6 and 0 the indication of value, field 5", used "PROEKULS" on small letter piece, very fine, expertized Dr Petersen BPP, very rare offerd stamp, Michel 1.400.-