This full-flavored, buttery, nutty cheese with characteristic holes is aged at least 60 days. Interestingly, American cheesemakers, not Swiss, modernized Swiss production. About 50 years ago, the only way to protect Swiss wheels as they ripened was to allow a hard rind to form. The advent of plastic packaging, which keeps moisture in but allows carbon dioxide to escape, made it possible to produce rindless Swiss cheese in blocks. Rindless blocks were developed for better yield in foodservice; retailers appreciate the higher yield and ease of cutting.