Lloyd’s Register/ International Maritime Organization (IMO) numbers

Prior to 1963 all ships recorded in the Lloyd’s Register of Ships were given a sequential number that varied each year according to their position in the sequence. Additions, deletions and renamings would affect the alphabetical position of any particular ship and thus their sequential number.

In 1963 it was decided to identify all ships recorded in the Register of Ships by a unique six figure number which was to remain bound to the relative ship throughout its life, irrespective of conversions and name changes, and never to be re-applied to another ship. For example, if a ship is converted and a new forepart added, the LR number remains with the engines, usually the aft section. The base numbers used for the initial coding exercise for the LR number were those in the Supplement to the Lloyd’s Register of Ships for 1963/64, a year which had the main register commencing with 00001 A. A. Cowan, and ending with 39966 Zyrianin while the supplement held numbers in the 4xxxx format for subsequent entries.

This base number was prefixed with ‘5’ to make it a six figure number, with ships ranging from 500001 to 54xxxx. All ships appearing in the 1963/64 edition of the Register were given a unique number, thus older ships were in the sequence 500001–539966, and new ships and renamings in the sequence, starting 54xxxx.

The 1964/65 Register of Ships retained the sequential number but also published the LR number in column 2.

From 1964 onwards new vessels were issued with numbers beginning 64xxxx. Until the 1971–1973 Register Books it was easy to identify the year of build of a vessel by its LR number; the new vessels being issued with LR numbers, the first two digits of which indicated the year of build, i.e. Border Battler built in 1968 has an LR number of 6803375.

Any older vessels not previously recorded with an LR number within that year’s sequence, i.e. a vessel identified in 1970 would be issued with a 70xxxx number even though her date of build may be 1958.

During the period 1971–1973 it was decided to assign LR numbers when firm contracts between shipowner and shipbuilder had been signed rather than on the completion of the vessel. Thus from that period until 1991, when the process ceased, the first two digits of the LR number became an indicator of the year of order, unless it was an older vessel not previously known. In 1991 it was decided to assign LR numbers in sequence regardless of date of build or order to ensure we would not run out of numbers in 1999.

The 1969–1970 edition of the Register of Ships was the first to show the check digit, thus making the LR number a seven digit number.

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