Quarantine "yellow jack" but this was also a name for yellow fever, which probably derives its common name from the flag, not the color of the victims (cholera ships also used a yellow flag). The plain yellow flag ("Quebec" or Q in international maritime signal flags) probably derives its letter symbol for its initial use in "quarantine", but this flag in modern times indicates the opposite—a ship that declares itself free of quarantinable disease, and requests boarding and routine port inspection. Australia has perhaps the world's strictest quarantine standards. Quarantine in northern Australia is important because of its proximity to South-east
Götheborg (ship) ordinary, rectangular flag. Swedish warships, or ships carrying a military commander, fly the Swedish ensign a triple-tailed or swallowtail and tongue version of the rectangular flag. The Swedish East India Company displayed a fork-tailed or swallow-tailed flag on their ships. The intention was that the ship should resemble a warship and thereby not attract pirates. This was against the rules and regulations for flags at that time. The use of the swallowtail was prohibited in a royal decree in 1751, but the SOIC ignored this and ordered their flags in Canton instead. In a memorandum to the Riksdag in 2012,