International Code of Signals (Overview)

The International Code of Signals was first drafted in 1855 by the British Board of Trade and subsequently published in 1857 as a means of maritime communications. The original publication showed 17,000 signals using 18 flags, part of which was specific to the United Kingdom and another part that contained universal signals to be used by all nations. Adopted by most sea-faring nations, the system was revised in 1932 to include seven languages: English, French, German, Italian, Japanese, Spanish, and Norwegian.

The Fourth Assembly of the Intergovernmental Maritime Consultative Organization revised the code in 1965 which became effective on January 1, 1969. This revision added Russian and Greek to the languages already included and adopted a new radiotelephone code. Each signal has a complete meaning.
Jorge Candeias, 31 August 1999

I asked a Flagmakers firm ("Industrial Velera Marsal S.A.") and they make 3 sizes measuring: 1.98x2.41 m, 1.37x1.68 m and 0.76x0.91 m, which they assure are "official". I didn´t find any proportions kept at the 3 sizes. They are close to 8-10, but a little more "squared" than that.

Maritime letter flags, as far as I know, go back to Sir Home Popham, who published "Telegraphic Signals or Marine Vocabulary" in 1800, with a larger version in 1803, and another expanded edition in 1812.

This was used by Nelson to signal his fleet before the beginning of the battle of Trafalgar, the 21 of October, 1805, the famous message: "ENGLAND EXPECTS THAT EVERY MAN WILL DO HIS DUTY". Certainly those flags were 1-1 in proportions and can be seen in several books.

After many manuals and codes, the actual international signal flags developed from Captain Frederick Marryat´s "Code of Signals for the Merchant Service".

This act