Timothy Barber hails the engineering genius behind Jaeger-LeCoultre’s Reverso watch, which is celebrating its 85th anniversary this year.

Were you to assemble a group of watch collectors in a room and ask them which Swiss brand was their favourite, I’d lay odds on Jaeger-LeCoultre coming out top a good amount of the time.

Sure, there are manufacturers that carry more clout and who garner more mainstream glory, but it is precisely for its slightly fringe appeal, tied to a historic flair for invention, that Jaeger-LeCoultre is cherished. Hardly an outsider at the ball, it’s also never quite centre stage – it’s that bit more specialist, and that suits it, and its fans, very well.

Its most famous watch, after all, is of a startlingly eccentric design – a rectangle that slides to the side and flips over in its case, giving it its name, the Reverso. It turned 85 this year – the idea, in 1931, came from a request from British army officers in India for a watch that could be worn while playing polo, and have its dial protected. I’ve often wondered why it was so important to wear a wristwatch at all in the heat of a polo match (it’s not as if it could be read while the dial was flipped over) but, then, I’ve also seen no evidence that it was ever used thus.

More important is the quiet brilliance of the Reverso’s execution, both then and now. The reversing case is a thing of micro-engineered joy, and a satisfyingly ergonomic distraction for idle fingers – so clever is its construction that, unlike many luxury watches, it’s practically impossible to fake – while the design as a whole is a classic of the art deco style.

There have been scores of variations, but the essentials remain constant: a rectangular case engraved with three notches above and below a dial that tends to be simple and austere, but with a hint of Jazz Age pep – particularly in classic models in which hour markers thrust into the dial like daggers.

A major plank of the Reverso’s early success was the possibility the reversed case offered for personalisation. On its flat surface could be secret engravings or enamel paintings – a coat of arms, a portrait, a personal message – that would be seen only when the watch head was flipped. That’s still the case – Jaeger-LeCoultre runs a special service for Reverso customisation that includes an online portal and, in its London Bond Street boutique, as of this year, a bespoke service offering all manner of decorative options. Want a pink dial on a green strap with a relief engraving of your dog? Why, you have only to ask.

At the same time, the Reverso has morphed far beyond its original format. For the deep-pocketed, Jaeger-LeCoultre has dreamt up a universe of complex masterpieces, including gyroscopic tourbillons, skeletonised minute repeaters, and other complications that reflect the brand’s technical genius, should you have six figures to spend.

The mainstream Reverso has evolved, too; while rarely considered as such, it has become, essentially, a travel watch. Rather than a blank reverse side fit for engraving and decoration, most modern versions offer instead a second dial for an additional time zone, meaning you can have one side set to the time where you are, and the other the time back home.

Fitting a watch movement into a case small enough to be flipped on the wrist and worn comfortably is no mean feat; making such a movement with a dial on either side, each able to be set to a different time (even on very slim women’s models) is a watchmaking marvel that is rather under-recognised.

Such “Duoface” watches now account for most of the Reverso collection, which currently stands at 37 models. My favourite of this year’s anniversary models throws in a full calendar display for good measure. The Reverso Tribute Calendar is cased in pink gold, and its dial shows the day, date, month and phase of the moon, besides the time, while on the reverse is the second time-zone dial with a lovely day-to-night indicator. It’s as exquisite and as singular as Jaeger-LeCoultre’s best watches tend to be.

Timothy Barber is The Telegraph’s watch editor.