Michael J. Fox wears a Casio CA-53W

Robert Zemeckis and Bob Gale sent Marty McFly to 2015 in Back to the Future Part II, a future of hoverboards, self-lacing Nikes, and holographic billboards, but they left his wrist in the present. Michael J. Fox wears a Casio CA-53W, the calculator watch Casio has sold since the 1980s: a digital timepiece with a tiny four-function calculator under the dial, the kind of thing that cost about $25 off the shelf.

The CA-53W had a brief run as a piece of the future you could actually buy, back when doing arithmetic on your wrist still felt like science fiction. Casio never really stopped making it, and a near-identical version is still in the catalogue today for roughly the same price.