E.M.C. Barraclough, the internationally renowned vexillologist writes ‘although at first ‘Jacks’ were flown from the mast-head of a ship, it soon became the practice to fly them from the ‘sprit-mast’ which was fixed to the bowsprit. It was often been thought that the “flag” is called a “Jack” because it flies from the ‘Jackstaff’, but actually the ‘staff’ is called a “Jackstaff” because the “Jack Flag” flies from it. Likewise, the British “Union Flag” is most often wrongly referred to as “Union Jack”
Most countries use the diminutive of their National flag as ‘Jack’
Scandinavian countries State flags and Jacks are 'swallow-tailed' or 'split' at the fly.Some countries have/had a ‘historic’ or other special design ‘Flag’ for use as ‘Jack’.
The Great Star Flag 1837
An 1818 act established that the Great Star Flag include a star for each state and 13 stripes. Capt. Samuel C. Reid, a naval hero of the war of 1812, recommended arranging the stars into one 'large Star pattern', a common design in the 19th. century.
Greece has two Flags, one with the simple ‘Greek Cross’ on blue field used as ‘Jack’ and the other with the ‘Greek Cross at the canton and nine blue and white stripes’ used as ‘Ensign’
The U. S. Coast Guard Ensign and JackThe badge has the motto ‘Semper Paratus’ (Always Prepared) and the date ‘1790’. The post card commemorates the 175 th. Anniversary of the U.S. Coast Guard.