Color advertisement from Jantzen Knitting Mills, Inc. in Portland, Oregon for a Jantzen swimsuit. The ad features a young woman wearing a strapless light blue one-piece swimsuit. In the background, a young man wearing red swim briefs is balancing on his hands and head. A small image in the bottom left corner depicts the head of a woman modeling a Jantzen swim cap.

Carl Jantzen and Roy and John Zehntbauer founded the Portland Knitting Company in 1910 with wool suits made on hand-knitting machines. The popularity of the suits became a catalyst for the company's name change in 1918 to Jantzen Knitting Mills.

Lastex is an elastic yarn in which a natural fiber (cotton, silk, etc.) is wound around a thread of latex, providing one- or two-way stretch to garments. It was registered as a trademark in the U.S. in 1931.