Since 1989, Casio is said to have sold well over 100 million units of a single digital watch model. That watch, the Casio F-91W, is still available at just over US$20 today. The F-B100W has a step tracking display up top that differentiates it from the old F-91W CasioStep tracking obviously isn't new, and Casio's been doing this on a number of its models for several years. What makes it special here is that it's available on a watch with a classic design that's instantly recognizable and beloved by millions around the world. Find the Casio F-B100W on the company's site, and the original F-91W over on Amazon US.