For a short while the US Navy has a special class of flags dedicated to Morse Code. Using three colours of red, yellow, or blue; the dits and dahs of Morse Code were distinguished with these flags.
Although they are no longer in use, as the ICS Maritime flags have taken over, they are interesting relics of once official flags.
The dits are represented by the colour red, while dahs are represented by the colour yellow. Blue is the special colour that can be a dit or a dah. The rule for blue is that its identity is determined by the preceding colour towards the hoist. This is on the left in the standard model, but is on the right when looking from the anterior side.
These flags were in limited use during the early 1900s. Finding one, would be of great value as they are extremely rare.
They are a first of their kind of
Tele-morse-graphic flag. Innately confusing the the eye that is unfamiliar with Morse Code, it was perhaps due to this property, that the ICS flags became the norm for the US NAVY. Note that ICS flags are often called Morse Code flags, which makes little sense since ICS flags have no direct connection to Morse Code.
These 'Retired US Navy' flags are at their base architecture and design, intimately reflective of Morse Code. And deserve to be called Morse Code flags more so than ICS flags.
Note that for the letter M the Morse code flag is shifted to horizontal axis. Obviously this was done to distinguish this flag from the ICS Number 5 flag. Otherwise, it'd be a confusing situation. A similar type of confusion still exists with our script between the letters and numbers 1 & l and O and 0. It is easy to make a mistake as these letters and numbers can be confused. This is also the case with ICS 5 and K, they are the same pattern and could look the same from a distance, to some extent.
Below is a modern extrapolation of the Old US Naval Code to numbered, Morse Code Pennants. Although they were never issued in this format, the basic principles of the patter still work. It was a simple design but since all the flags 'look-a-like' the Morse Code flags were not as effective as the contrasting symbols and colours of ICS standard flags.