The specialty area of United States Revenues may be the most fertile collecting specialty for collectors. Scott lists the general issue revenues which are interesting enough. But it is in the field of the specialty revenues where collectors have had the most fun. There are specialty Revenues for everything from Perfume Tax Stamps to Consular Office Revenues (which paid the tax on things like passports and visas), to even Marijuana Tax Stamps (which paid a tax on the illegal drug). Incidentally, Marijuana Tax Stamps were declared unconstitutional by the the Supreme Court as a form of self incrimination since it was illegal to sell marijuana without buying the stamps and paying the tax. But since it was illegal to sell pot anyway, this was ruled law enforcement double dipping. There are over thirty specialty revenues that the Scott catalog lists, and scores more of Scott unlisted revenue types