1) Two garments in one 
A frock coat is a man`s coat characterised by a knee-length skirt (often cut just above the knee) all around the base, popular during the Victorian and Edwardian periods. The double-breasted style is sometimes called a Prince Albert (after the consort to Queen Victoria). The frock coat is a fitted, long-sleeved coat with a centre vent at the back....
[n] - a man`s coat having knee-length skirts front and back
noun a man`s coat having knee-length skirts front and back; worn in the 19th century
a man's close-fitting, knee-length coat, single-breasted or double-breasted and with a vent in the back.