The Democratic People’s Republic of Korea (DPRK) issued its first set of stamps on September 19, 1948 commemorating the establishment of the DPRK on September 9, 1948, Scott 14-15. The Scott numbers for North Korea 1 -13 are for used for the Soviet occupation era. Since those stamps were issued, North Korea has issued stamps commemorating the formation of the DPRK every 10 years as anniversary issues.
This author has a question about the scene depicted on the 40th anniversary souvenir sheet, issued in 1988, Scott 2776, and then again the same scene is depicted in the 60th anniversary souvenir sheet issued in 2008, Scott 4783. The design of the two souvenir sheets is similar in that it depicts Kim II Sung presiding over the design/choosing of the DPRK flag and national emblem. Interestingly, on the 1988 souvenir the event is described in English, but not on the 2008 souvenir sheet.