In 1976, the DPRK released several souvenir sheets that differ (within the same catalog number) from each other. Differences in size, perforation, presence of glue, etc. can be found. The information in catalogs is somewhat different. The most notable example would be the Souvenir Sheet for release: Winners, 21st Olympic Games, Montreal.
MICHEL catalog: Stamps 1976: Winners, 21st Olympic Games, Montreal, nos. 1516-1521, souvenir sheet №. 27, perforated L 10 ¾. Souvenir sheet size: 109×84 mm. SCOTT catalog: Souvenir Sheet #1482. Imperf.