4 Shilling, dark yellowish green in single franking, on under-franked folded letter cover, the stamp is in perfect condition and fastened original on the folded letter cover, cancelled by blue dual circuit cancel "Hamburg ST. P. 27 / 7 67" to Rotterdam, at the bottom "franco" cancel in cursive handwriting, blue mounted, with "3" in blue indelible pencil for the to calculating postage due, reverse dual circuit cancel from Rotterdam in red mounted as arrival postmark, left above the cancel the mailing North German Insurance company, rare cover from whose known correspondence, very fine, despite still visible lateral and longitudinal fold, visually very attrative copy, in unsigned condition