The fashion illustrations here date from 1964. They feature shaped wool suits with bold checks. It's hard to think of a more classic 60's wool than hounds tooth, and here it is in full splendor. As examples of mid-1960's fashion, 3/4 sleeves (worn with long gloves) are almost equal to the short jacket length. The rolled collars are heavily interfaced to achieve that carefully curved line. The jackets probably have self covered buttons, in a bold, large scale typical of the Jackie O era.
Most likely drawn using colored chalk on an egg shell finish bond paper, these drawings have a glowing effect achieved by carefully controlling the lighting. For illustrating checks, these illustrations offer great inspiration and show how to not over-draw the details, rather how to suggest an overall effect to a better advantage.
When I can indentify the illustrator, I'll add that information here.