This is vintage dresses from era 1960s'-1970s' drawing and may be can help you guys to separate an era.
In the pictures on this page you see a selection of early 1960s slender column sheath dresses. These styles had to a certain extent been in fashion in the 1950s, but there are style elements that make them quite peculiar to the 1960s.
The hairstyles are very much in the vogue of hair style fashions after 1960. The dresses all rest on the knee and are all paired with sharp pointed stiletto toe shoes. Hemlines had been gradually creeping up from around 1960. Three quarter and elbow length sleeves were very much a style feature of 1961/1963. Softer lines are also evident with several dresses having bloused bodices. However a dress style such as this demanded a slim figure and a good corselette.