"...The chesterfield is the most formal and classic town coat a gentleman can own. It was originally a variation of the basic Victorian frock coat, whose skirt descended straight to the bottom hem--in either a single- or a double-breasted version--but, unlike the frock, had no waist seam. It was named for the sixth Earl of Chesterfield (not the famous fourth earl, who wrote all those instructive letters to his bastard son), a leader of fashion among the Regency dandies who strolled Bond Street in the early years of the nineteenth century. He probably didn't invent the velvet collar--the coat's trademark. But he was certainly a great popularizer of the style, because when he died in 1866 his name had already become common coinage for the garment.
By the turn of the twentieth century, the chesterfield had assumed the classic lines and details it retains today: a full-length (which at the moment means to the calf) usually single-breasted coat with fly-front closure on the single-breasted version, shaped body, velvet collar, center back vent, two side pockets and set-in sleeves. As the dressiest of town coats, it's usually tailored in dark blue, dark gray or black patternless wool or cashmere. Variations, though limited, include patterns of self-striped wool and herringbone tweed in brown, as well as gray and blue. The most popular variation these days is the chesterfield done in fawn (a marled greenish tan) covert or whipcord twill, with either a bottle green or dark chestnut brown velvet collar. The velvet collar cover--whose color is intended to quietly complement rather than contrast with the coat's color--is not only a bit of discreet adornment, but was, in an age when men wore their hair longer, a practical way of dealing with soiled collars: it's easier and cheaper to replace the velvet cover than to dispense with the entire collar..."