(as) fine as Dick's hatband

(as) fine as Dick's hatband

Very good or nice; exceptionally fine. The "Dick" in question is unknown, though rumored to be Richard Cromwell, who served as Lord Protector of the Commonwealth of England, Scotland, and Ireland in the mid 17th century. Why, that dress is as fine as Dick's hatband—you look just lovely, my darling.
See also: fine, hatband