Sack coat. It had no shaping at the waist like the other coat styles and instead hung straight down to mid thigh or above with a single breasted row of buttons to hold it in place. It came about in the 1850′s and gradually became the primary day coat style into 1900. It differed from modern coats by buttoning up very high, although it was common only to wear the highest buttons buttoned and the others open. It was a country look, not proper enough for city gentlemen until after 1900.