Thanks a lot Thierry for your reply, I did learn some new things
But one question: When you say the code on the wing undersides represents an aircraft's identity, is this a tactical I.D. like the fuselage codes on the British or German aircraft (squadron codes or Verbandskennzeichen) or part of another registration system I don't know yet?
BTW: Maybe these photos help to identify the location (They were taken at the same spot. Other images show both planes together)