Ship Classification : Why is it called classification?

In the second half of the 18th century, marine insurers, based at Lloyd's coffee house in London, developed a system for the independent inspection of the hull and equipment of ships presented to them for insurance cover. In 1760 a Committee was formed for this express purpose, the earliest existing result of their initiative being Lloyd's Register Book for the years 1764-65-66.

At that time, an attempt was made to 'classify' the condition of each ship on an annual basis.
The condition of the hull was classified A, E, I, O or U, according to the excellence of its construction and its adjudged continuing soundness (or otherwise). Equipment was G, M, or B: simply, good, middling or bad. In time, G, M and B were replaced by 1, 2 and 3, which is the origin of the well-known expression 'A1', meaning 'first or highest class'.
The concept of classification caught on around the world. Bureau Veritas (BV) was founded in Antwerp in 1828, moving to Paris in 1832. 'Lloyd's Register of British and Foreign Shipping' was reconstituted as a self-standing 'classification society' in 1834; rules for construction and survey were published the same year.
Registro Italiano Navale (RINA) dates from 1861; American Bureau of Shipping (ABS) traces its origins back to 1862. Adoption of common rules for ship construction by Norwegian insurance societies in the late 1850s led to the establishment of Det Norske Veritas (DNV) in 1864. Germanischer Lloyd (GL) was formed in 1867 and Nippon Kaiji Kyokai (ClassNK) in 1899. The Russian Maritime Register of Shipping (RS) was an early offshoot of the River Register of 1913. More recent foundations have beenYugoslav Register of Shipping (now the Croatian Register of Shipping (CRS)) in 1949, China Classification Society (CCS), 1956; Korean Register (KR), 1960; and Indian Register of Shipping (IRS), 1975.

As the classification profession evolved, the practice of assigning different classifications has been superseded, with some exceptions. Today a ship either meets the relevant class society’s rules or it does not. As a consequence it is either 'in' or 'out' of 'class'. However, each of the classification societies has developed a series of notations that may be granted to a vessel to indicate that it is in compliance with some additional criteria that may be either specific to that vessel type or that are in excess of the standard classification requirements.