Use of the Royal cypher on post boxes

Since their introduction in 1853, post boxes have carried the insignia, or cipher, of the monarch reigning at the time of placement.

The most common cipher that you will see on current post boxes is the EIIR mark of Queen Elizabeth II which features on more than 60 per cent. Around 15 per cent of current boxes are from the reign of George V and then in descending order, George VI, Victoria, and Edward VII. There are 171 boxes surviving from the short 1936 reign of Edward V.