This had been the cover of a 1989 set.  It’s just the cover, and was made to include two actual postcards (connected, as you see):  one of the museum, a former royal palace, in Phnom Penh; and one of a bas-relief Apsara at Angkor Wat.  When fully open, this measures 5-7/8″ x 10-1/2″.  Grade: 1