I have a copy of a formerly classified signal giving ships names in a convoy - each ship followed by a four digit code. Would this be a one off, one convoy, call sign? example Rangatiki 4250
According to convoyweb, merchant ships had signal letters: http://www.convoyweb.org.uk/signal/index.html You might have better luck posting in the war at sea thread?
Merchant ship's four letter signal letters were just that - letter flags: British ships began with a G or an M. I have been waiting to see what others say about a four figure signal, convoy position numbers were normally two or three figure, denoting the position of the ship within the convoy, the first figure was the ship's position in the row, numbered from the left (port for the nautical types) and the second the row number. 4250 would have been an enormous convoy!.