Welcome to “Watches You Should Know,” a bi-weekly (the once-every-two-weeks kind) column highlighting notable watches new and old that have interesting stories or have had a surprising impact on the industry.

The brilliant horological innovations of historic watchmakers like Huygens and Breguet, past generations’ quest for ever greater precision and accuracy, the centuries of mechanical refinements and craftsmanship…were they all leading to this? It costs almost no money and looks like it could have come out of a gumball machine, but the Casio F-91W watch is an astoundingly reliable timekeeper and outperforms fancy mechanical watches at almost every metric.

This sub-$20 plastic watch is perhaps the ultimate representation of how the proud Swiss mechanical watch industry was undermined and nearly destroyed by mass-produced, plastic-cased, quartz-powered watches. Call it a throwaway watch or a toy, but the accuracy, functionality, and durability it offers for such a price deserves some sort of recognition — and puts the whole rest of the watch industry into sharp perspective.

While the F-91W may look like a primitive precursor to the classic, square-cased G-Shock DW-5000C released in 1983 (its legacy alive in today’s 5600), in fact the reverse is true. Introduced in 1991, the F-91W probably owes some of its design to the G-Shock’s success, but it was likely also influenced by similar technical constraints. The F-91W has remained in continuous production, and today about 3 million units are made annually.

Mere quantity and affordability, however, don’t fully explain its success: design, functionality, and ergonomics also contributed to the F-91W becoming the representative of a “cheap digital watch” and cultural icon. It has been the subject of art, and co-founder of London’s Design Museum and design critic Stephen Bayley calls it a “modest masterpiece,” according to the BBC. Around 3,750 Amazon users currently rate it 4.5 out of five stars. Its unpretentious status has been somewhat eroded by hipsters adopting the F-91W (and other cheap, nostalgic Casio watches like the calculator and world time models) as an ironic fashion statement — but even that speaks to the success of its simple design.

The Casio F-91W has three buttons and a remarkably clever amount of functionality for its price, size, and simplicity. It takes about four seconds to learn how to use the stopwatch feature that itself has a couple different options — some people have made a game out of trying to stop the counter as close to zero as possible, which is tough, since it measures down to 1/100th of a second. You can quickly toggle between 12- and 24-hour displays, set alarms, and more — all genuinely useful features, and nothing extraneous. Casio’s promised accuracy of +/- 30 seconds per month means about +/- one second of accuracy per day, which almost no luxury mechanical watch can compete with.

Emblazoned across the bottom of the watch’s face is a “WR” logo flanked by “Water Resist.” For the record, this is equivalent to the 30m (3ATM/100ft) water-resistance standard many watches use to indicate that it is not intended for swimming, showering, and the like. Neither can you pound it with a hammer. With reasonable daily use, however, as well as a battery change every seven to ten years, a Casio F-91W can be expected to last a long time. It’s even easy to change the 18mm strap, if necessary or desired.

Shown here is the most basic and ubiquitous variant in black plastic with the blue highlights known as the F-91W-1, but other F-series versions feature different colors and case materials like silver and gold. These are notably small watches for today’s standards. The Casio F-91W measures 37.5mm by 33.5mm by 8.5mm and weighs only 85g, according to Wikipedia — and not every watch model out there has its own Wikipedia entry, further speaking to the F-91W’s specialness. This is an extremely comfortable watch to wear that simply and unobtrusively does its job well.

If you can appreciate the value it offers, the F-91W is even charming. Hold down the button on the lower right side for three seconds, and the LCD screen will read “CASIO” in place of its normal display (originally a way to authenticate the watch against counterfeits). The Casio F-91W can be enjoyed as a carefree and reliable tool or culturally significant art and is available anywhere in the world, usually for between $10 and $20.

This Is How G-Shock Watches Are Tested and Built

In the early ’80s, after accidentally destroying his mechanical watch, Casio’s head of watch design Kikuo Ibe challenged himself and his team to build an indestructible watch. What seems like a high-school physics project eventually birthed the original G-Shock, one of the most iconic watch lines in timekeeping history. Read the Story