Blue Ensign of the United Kingdom.
The ships of the Royal Navy were traditionally divided into three (3) designated squadrons; red, white, and blue which were the colors of the Union Jack. By 1864 naval tactics had eliminated the squadrons resulting in their flags having new uses. The Royal Navy kept the white ensign, because Viscount Horatio Nelson had brought it glory at the Battle of Trafalgar. The red ensign was to be used by merchant ships.
The blue ensign was reserved for vessels operated by government departments such as the Post Office. Later, armed or unarmed vessels of British colonies were also instructed to display the Blue Ensign. In all cases the badge or emblem of the department or colony was to appear in the center of the fly end of the flag. Without a badge, only merchant ships commanded by officers in the Royal Naval Reserve wore the Blue Ensign.
This example does not seem to be one designed for or used on a ship; Its size is too small and it is printed rather than pieced and sewn throughout. Additionally it is lacking the heading with rope or clips usually found on all British naval flags. Instead it was probably attached to a staff and waved or flown as a patriotic flag, perhaps during World War I.
ZFC Noteworthy Flag
Sources:
THE COLOURS OF THE FLEET, The Flag Institute, 22 April 2012, from: http://www.flaginstitute.org/pdfs/the_colours_of_the_fleet.pdf
Blue Ensign, Wikipedia, 29 May 2012, from:
http://en.wikipedia.org/wiki/Blue_Ensign
NATO, Wikipedia, 22 April 2012, from: http://en.wikipedia.org/wiki/NATO
United Kingdom: the Blue Ensign, Flags of the World, 29 May 2012, from: http://www.crwflags.com/fotw/flags/gb-ensw.html
Image Credits:
Zaricor Flag Collection
RTZFC
