Code Letters Official Numbers were a forerunner to IMO Numbers. Empire Buttress and Wallsend had the United Kingdom Official Number 168959. Bordagain and Daring had the Liberian Official Number 1475. Empire Buttress and Wallsend used the Code Letters BFKP. References 1943 ships Ships built on the River Tees Empire ships Ministry of War Transport ships Steamships of the United Kingdom Merchant ships of the United Kingdom Steamships of Liberia Merchant ships of Liberia Maritime incidents in 1955