1928. DANMARK. Air Mail. Slotmaschine (automat) 4-stripe with 7 øre Christian X + 3 øre pearlgray + 7 øre Christian X + 3 øre pearlgray on beautiful small LUFTPOST cover Nattflygningen till London with Swedish cancel LUFTPOSTEXP. Nr. 1 FJÄRDE TUREN STOCKHOLM-LONDON 29-VIII-28. AIR POST OFFICE STOCKHOLM-LONDON OVERNIGHT SERVICE 29-30 AUGUST 1928. Reverse arrival cancel AMSTERDAM 30 VIII 28 PER LUCHTPOST AANGEBRACHT. Rare franking.