The SCOTT Stamp Catalogue attempts to list and assign stamp numbers in chronological order for commemorative stamps; except that, it tends to group "Series of stamps" at the first year of issue. It also, periodically lists "definitive stamps" and any respective "Coil stamps", by a group of stamp numbers (SCOTT calls them, "Blocks of numbers") inserted about every five-years of issue.

Souviner Sheets, are normally assigned a minor-suffix of "a", to the stamp number assigned.