Code letters

[3] The first vessel to be reported in Lloyd's List by her letters was the Mallard (LDPN), off Deal, Kent whilst on a voyage from London to Calcutta, India.

By the 1860s, individual ships were being allocated code letters in the United States and Europe.

For example, the ship Heinrich Arp: Code Letters "RDWL" (1923-34) were changed to Code Letters "DHKV" (1934-45) and from 1946 once more to the Soviet Union Ship's call sign (unknown, but first character was "U").

in this book (or disk) mentioned: "Call sign formed from the international call sign series in accordance with Article 19, Section III of the Radio Regulations (RR).

"[6][7] Some canals or narrow places have special requirements for the vessels to hoist their call sign flags during the transit through the area.

Thanks to technological advances in the navigation abilities of marine craft, this action is no longer compulsory.