Official Numbers were issued to all British seagoing vessels extant in 1855,
in order to give each ship a unique identity – there were hundreds of ships
with names like MARY. The same number remained with the ship throughout its
life, despite changes of name or Port of Registry (POR), as long as it remained
on (or returned to) the British register – which included the British colonies.
In 1855 each British port was given a block of numbers to allocate in turn
to each (existing) ship clearing (leaving) that port, e.g. London received
1-999. Thereafter every ship added to the British register, either newly
built or acquired from ‘foreigners’, was given the next number from the sequence
for her POR.
ONs are useful for indicating if two apparently similar ships are actually
the same, they indicate a date of completion (for new ships after 1855),
they show what was the first name a ship held and they may be the only clue
as to a ship’s identity, e.g. on a seaman’s discharge papers.
The Mercantile Navy List lists alphabetically all vessels registered at the
start of each year from 1857 annually until 1976 (apart from 1941-46), including
Name, POR, ON and Tonnage (usually net). Editions from 1873 gave further
information such as Owner and Place and Year of Build. The first MNL was
issued in 1857 (a reprint is available from Elibron Books), and also included
a ‘decode’ list, i.e. a list in ON sequence, but this latter was dropped
after 1864. The only known complete list of all ONs in sequence is the Appropriation
Books kept by the Registrar General of Shipping & Seamen (now the Maritime
& Coastguard Agency). These books are due for transfer to the National
Archives. Number 100000 had been reached by about 1892 and 199900 by about
1957. Numbers 200000-299999 were allocated to the United States, while from
300000, many blocks were allocated to former British colonies, for some of
which the MCA has no detailed record.
It is possible to create computerised lists of ONs by typing in data from
MNLs – a large job since there have been around 300000 British ships. Ted
Finch has developed a list of Number and Name for simple look-ups of British
and US ships from about 1890. Gareth Butler, assisted by Ian Buxton, has
been working on a much larger table of ships before about 1890. He has input
some data for about 40000 ships using sources such as MNLs. It is intended
that each change of identity, e.g. of name or POR, will get a new row, if
possible with the date the identity was adopted, whether new built, bought
foreign etc. Although there is a long way to go yet, it has been possible
to produce an interim table covering many ships with ONs below 100000, with
ON, Name, Year Identity Adopted (where known), POR, Tonnage (Net and Gross
where known). For sailing ships, gross and net tonnage were close, but for
steamers gross is larger than net as it includes machinery spaces. However
the entries have not been fully checked for duplicates, misspellings or dubious
tonnages, while further editing is needed for information included in the
Name column. Many of the further identities have yet to be added, so note
that Year may refer to a change of POR rather than a year of build. It has
been considered more useful to make this incomplete table available, while
work continues on extending it.
For larger British built ships, a further source is the Global Ship Number
system at Newcastle University. This is a useful ‘first port of call’ to
see if a ship existed, with basic data, fate and ON. Searching is possible
by ON as well as Name. See: http://gsn.ncl.ac.uk