For those who want a truly custom-made timepiece, it'll cost you - and even if you're prepared to pay, you might not be allowed into this exclusive circle. Luxury watchmakers have been discreetly offering their bespoke services to collectors who wouldn't mind a hefty price tag or a year or two of wait.

Curiously, however, plenty of the respected watch manufacturers would rather keep the service off the radar, claiming that it's reserved for their most loyal patrons and VVIPs. "We do it very exclusively. It's almost like we don't talk about it," says Jean-Christophe Teigner, Roger Dubuis' global associate director of customer marketing.

The compelling rarity has only fuelled seasoned rare collectors' desire to join the elite club in recent years, and their piqued interest is evident in the amount they're willing to pay for a customised timepiece. At Christie's Geneva Important Watches auction last November, a unique Patek Philippe platinum observatory chronometer especially made for late criminal defence attorney J.B. Champion fetched almost US$4 million - a world auction record for a watch without complications.

Watchmakers have taken note of the growing demand for personalised models. "There has clearly been a trend," says Octavio Garcia, chief artistic officer of Audemars Piguet. "It's due to the relationship that grows between us and our clients as they feel more comfortable with the brand. For us, it opens a possibility to this kind of collaboration."

Arnaud Bastien, regional director (Asia) of high jeweller Graff Diamonds, echoes the sentiment, and Roger Dubuis' Teigner attributes the cause to a more mature base of clientele.

"Clients who buy our watches aspire to more than just the object, but the whole experience," he says. "They want to be part of the story. To be able to have their personal touch is very much in demand."

Vacheron Constantin recognised the importance of this growing demand in 2007 and consolidated its bespoke orders by establishing the Atelier Cabinotiers department, made up of 10 artisans and headed by Dominique Bernaz. The department is an extension to the house's tradition of making bespoke watches since 1755. The department has about 40 bespoke projects on hand simultaneously every year.

"The ability of a watch company to manufacture one-of-a-kind timepieces for a private client is what makes the difference between horlogerie and haute horlogerie," Bernaz says. "It's important for us to keep the bespoke service to show respect to both our clients and our roots."

The level of personalisation starts from simple engravings to a completely tailor-made calibre. In many cases, the latter is what clients are most interested in.

At Vacheron Constantin, for instance, watchmakers can modify existing calibres or even develop a brand new movement from scratch for a client. Such orders can take years to complete - an order commissioned in 2007 for a personalised timepiece featuring a calibre of several complications is not expected to be ready until 2014.

Given the long wait, it's interesting to note that the finished unique pieces actually rarely see the light of the day unless the owner wishes otherwise.

Since the beginning of its Atelier Cabinotiers operations in 2007, Vacheron Constantin has only had two bespoke pieces documented in its archive, which shows the level of complexity and delicacy of the novelties. The Philosophia, for example, only has one hand to indicate the present hour, as the owner finds knowing time to the nearest minute to be of no use. The dial is calibrated for 24 hours, and the watch has complications, including a tourbillon, moonphase display and minute repeater.

Another piece known as Vladimir upgrades Constantin's limited-edition Calibre 2755, adding yet another extra function - the number of the calendar week - to its already complicated group of 16 functions. To the owner's liking, its flank on the rose gold case is engraved with the 12 Chinese zodiac animals.

If that's a bit too much detail for watch aficionados who desire personalisation, they can go for a modified version of existing models. One customer from Cologne, Germany, for example, made a special order with Parmigiani Fleurier, requesting a variation on the company's Transforma model, a watch that can be worn in three different ways. The watch head can be removed from its carrier and be used in a separate frame as a pocket watch with a matching chain or as a table clock. The client wanted a black-and-red dial with a more sporty touch. Newcomer Cvstos, despite its limited production capacity, is also answering to eager customers. It has launched the Challenge World Coat of Arms collection, offering customised gold-plated discs to be inserted on top of the highly skeletonised dial.

While the price and construction time for these unique pieces vary, for simpler decorative personalisation, there is a much more standardised breakdown. At Vacheron Constantin, adding a unique dial or individualised engraving on an existing model takes about 12 months. And the price is about 20 per cent higher than that of its serially manufactured counterpart.

For Cvstos' specially ordered dials, additional charges range from 2,000 Swiss francs (HK$16,390) to 10,000 Swiss francs, and it takes anywhere from one month to two years to complete, depending on the design's complexity.

The numbers may look good for the manufacturers at first glance, but the money and time spent producing unique watches is not as cost-effective as producing a series, therefore, few manufacturers are willing to offer customised pieces. "Being a manufacturer of this size, we are not in the position [of offering bespoke calibres]," says IWC's senior product manager Niklaus Fumasoli. "We need very strict planning in order for us to be commercially successful." Nonetheless, IWC offers customisations on aesthetics level for its Siderale Scafusia model. Each project will take a year to complete.

And, even if manufacturers do offer bespoke services, often for the sake of marketing and relationship-building, they proceed with caution.

Cvsto's co-founder and chief designer Antonio Terranova says the personalised parts are mostly decorative rather than functional.

"When I create something functional, like the Challenge Tourbillon [2007], I want to keep it for the brand," Terranova says. "We are able to do it because we are an intimate operation producing only 2,000 pieces a year, but sometimes a unique piece can also give you a bad reputation."

"Bespoke service is something we offer, and we are very careful with it," Audemars Piguet's Garcia agrees. "Our main goal is to develop products that reflect the brand's values, but we do have passionate clients who really want something distinctive for themselves."

Brands that are famous for their high jewellery, such as Cartier, Bulgari, Graff Diamonds and Van Cleef & Arpels, seem less reserved with the notion of customisation on the level of aesthetics.

"Special orders have always been a tradition for us," says Jean Bienaymé, Van Cleef & Arpels' international marketing and communication director. "We feel that as a high jeweller, it's part of our mission to create unique pieces." The high jeweller creates bespoke dials for clients on a regular basis across the globe.

"[A bespoke watch] is not necessarily more precious, but it offers different interpretations and customisations," says Pierre Rainero, Cartier's image, style and heritage director. "It represents 'something just for me'."

Graff Diamonds provides most types of personalisation, from a simple engraving to a hand-painted dial or special gem setting to house either one of its existing house-produced movements - GraffStar Grande Date and ScubaGraff.

Cartier can personalise the dial, case and straps for existing models. Special cases can also be made. The brand will be developing an exclusive mould and integrate its mechanical heart to fit into the case while meeting its quality standards. "For instance, one of the most important criteria is that the case must be waterproof," Rainero says.

The commission process at different high jewellers is somewhat similar. To place a customisation order, you can contact the staff at the local retailer. The order is then passed on to the headquarters, and a team of designers will communicate with the client to develop a blueprint. A deposit will kick-start the project, which can take six months to a year to complete.

While the sky's the limit, depending on how deep your pocket is when it comes to bespoke orders, there are still certain values that watchmakers won't compromise on.

"We want to deliver a positive message and value through each of the pieces with the best stones and best craftsmanship," Bienaymé says.

"You won't see us producing a snake motif or other aggressive animals, for example. The design has to be in line with the house's history and values that we believe in."