Gentleman's silk top coat, late 18th century
Throughout the 18th century, the essential features of a gentleman's costume—the topcoat, the waistcoat with or without sleeves, and knee-length breeches—did not change, but the shape slowly evolved. After 1760, topcoats like this one began to be cut away at the front and were seldom buttoned.
Despite the glacial pace of change in men's fashion over the period, subtle details on the garment could show if the wearer were in or out of fashion. This is because the style of trimming or the accessories changed more quickly than the basic shape. So the details on the garment were stylistically quite important.
The coat retains the large self-covered buttons, fold down collar, and wide cuffs of earlier coats. The buttons on the topcoat are decorative only; the coat closes in front with hidden hooks. The sleeves of the topcoat are cut with a curve to accommodate the elbow. http://vintagetextile.com/new_page_251.htm