This set has five maximum cards, of which four appear in the scan.  The full English caption (there’s also Thai) says:  50th Anniversary Celebrations of His Majesty’s Accession to the Throne (2nd Series).  Issued in June 1996 (Thai 2539) in honour of King Bhumibol.  There is some postmark ink transfer on the reverse of each card as they were stacked during processing.  We don’t consider this to be a defect.  Grade: 1