Black's Law Dictionary (2nd edition)dictionaries

A1

Of the highest qualities. An expression which originated in a practice of underwriters of rating vessels in three classes,—A, B, and C; and these again in ranks numbered. Abbott. A description of a ship as "A 1" amounts to a warranty. Ollive v. Booker, 1 Exch. 423.

Source: Black's Law Dictionary 2nd Ed (1910)