E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
means first-ratethe very best. In Lloyds Register of British and Foreign Shipping, the character of the ships hull is designated by letters, and that of the anchors, cables, and stores by figures. A1 means hull first-rate, and also anchors, cables, and stores; A2, hull first-rate, but furniture second-rate. Vessels of an inferior character are classified under the letters Æ, E, and I.
She is a prime girl, she is; she is A1.Sam Slick.