Three types of back vent (diagrammatic).
	(a) Back vent Of 1770's and 1780's; but sirrlilar, from 1700 to 1730, with the hip buttons widely separated.
	(b) Back vent with side folds; mainly 1730 to 1770.
	(c) Back vent with overlp ('tackover'); mainly 1780's and '7Ws.

 

 

original drawing by Barbara Phillipson, Phillis Cunnington