They are actually revenue stamps/seals. They are found on any item the government wants to collect excise tax on. Cigarettes, cigars, tobacco in many forms, playing cards and even marijuania in Canada. They come in several forms and sizes and are found perforated also. Attached is an example of the new cannabis issue.
James, something some of the people in the us have been waiting for since the embargo was put in. Cuban cigars that is. But now I believe their embargo has been removed so they can get them legally now.