A1
means firstrate—the very best. In Lloyd's Register of
British and Foreign Shipping, the character of the ship's hull is
designated by letters, and that of the anchors, cables, and stores by
figures. A1 means hull firstrate, and also anchors, cables, and
stores; A2, hull firstrate, but furniture secondrate. 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.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894 More on A1 from Fact Monster:
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