Every man worth his salt has a bag of electronic devices, old phones and miscellaneous wires and adaptors whose uses have long been forgotten. Digging through my own "mystery" bag, I found my old clamshell phone and reminisced about how they were the dominant form factor in days of old (five years ago).

Form factors also come in and out of style in the world of watches. Classic shapes such as round, square or rectangular may be more popular, but there is value in the rarity and unsung beauty of the tonneau.

Tonneau watches are a particular speciality of Richard Mille. Indeed, the brand has become synonymous with this form and the RM 037 Automatic (below right) is an example of its expertise. The titanium case is 52.2mm by 34.40mm, making this a pretty hefty watch, accentuated by its oversized crown construction and the eight titanium screws holding the case to the baseplate. The watch has an automatic in-house Calibre CRMA1 movement that powers hours and minutes, an oversized date indicator and an adjustable rotor geometry, which allows the rotor to adjust to the owner's activity level and hence affects the barrel wind speed. It may seem like gimmickry, but the technology is indubitably impressive. The dial design has been skeletonised, adding to the imposing nature of the watch, although the numerals blend into the skeleton, making it confusing and difficult to read. The Richard Mille RM 037 Automatic is priced at HK$566,000.

Vacheron Constantin, meanwhile, delved deep into its glorious horological archive last year to come up with the Malte collection, which celebrates a century of tonneau-shaped watches from the venerable Swiss atelier. The Vacheron Constantin Malte Small Seconds (left) is perhaps the least noticed member of the range, but its lack of pomp works to its advantage, as it shifts easily between dress watch and everyday statement piece. Coming in an 18-carat, pink-gold case measuring a relatively delicate 36.7mm by 47.61mm, the timepiece has all the subtlety you would expect from the brand. But what lies beneath the dial is the true gem. The Calibre 4400 AS movement powers hours, minutes and small seconds at the six o'clock position, with a very impressive 65 hours of power reserve. On top of that, the movement has been accorded the Geneva Seal, certifying the highest possible standard of finishing and decoration. The Vacheron Constantin Malte Small Seconds is priced at HK$210,000.

Frederique Constant, meanwhile, proves a masterclass in watchmaking need not mean a hefty price tag, with its FC-292M4T26OS (top right) priced at just HK$9,400. Despite the technocratic name, it is a classically designed watch inspired by the art-deco movement of the early 20th century, as evidenced by the dial face, which has plenty of charming and eccentric features. These include the retro styles of the hour- and second hands and the graphic design of the roman numerals. Indeed, the tonneau shape itself, with its offbeat curvature, is very art deco. The automatic FC-292 movement is robust and powers the standard hours, minutes and small seconds, along with a chronograph and date indicator. The case is made of stainless steel and measures 49mm by 36mm, making this a good size for formal or daily wear. Finishing off the look is an exotic ostrich leather strap.