Levi's advertisement from the September 1964 issue of Playboy via Vintage Ads and Stuff.
"Never, under any circumstances, let a girl borrow your White Levi's of Cone Corduroy. If she says she's going to a costume party and wants to go dressed as Huckleberry Finn, turn a deaf ear or lend her an old shirt. But don't part with your Levi's. Girls find long, lean, well-tailored Levi's irresistible. Especially in extra heavyweight corduroy. And if yours happen to be softened with age, so they look and feel like old leather, you're a goner."