The brand owned by Pabst today, but once it was the 4th largest brewer in the country. The famous rings stood for “Purity, Body, and Easy to Vomit Back Up,” and were reportedly the inspiration for John Bonham’s Led Zeppelin logo. And by "inspiration" I mean they asked him to come up with a logo, and after six months he hadn't, and it was getting close to the print date for the album cover, so he looked at what was in his hand, and said "use this here."

Or, he was thinking of molecular crystal Borromean rings.