Glen plaid is a twill woven pattern of small and large checks that form a sort of plaid-within-plaid pattern. It is usually made of tropical weight wool.
Glen plaid is one of those classic patterns that is always in fashion. The pattern is subtle enough to become a neutral and can be mixed with solids or prints.
From 1955, woman's suit with black velvet Chesterfield collar and pleated skirt by Moordale. Men's suit by Bloomingdale's. Click the picture for a larger view.