Card of a Boeing 737-800, and the caption has technical details.  The registration number, D-ABKC, confuses airfleets dot net, and confuses us too.  It may be that this aircraft is now with the Romanian airline Tarom.  Or maybe not.  Go see.  Three of these cards are available.  Two were mailed in 2011: one has two German stamps and partial postmark (Grade: 2, $5) and the other has three different stamps from Austria, also partial but illegible postmark (Grade: 3, $5).  The third was mailed in 2013, with stamp, postmark, and Priority label (Grade: 1, $5).