Most watch collectors would agree that owning a Patek Philippe timepiece entitles you to play in the big leagues of horology.

But, for added cachet, what if the watch face was the colour of Tiffany & Company’s signature robin’s egg blue and featured the retailer’s name? What if the model was a replica of the Ref. 5711, the steel Nautilus, one of the most coveted wristwatches in the world, which was recently discontinued?

Then you’d have the horological equivalent of a unicorn, whose hypothetical value could rewrite the record book for secondhand watch sales.

The luxury watch world had never heard of such a timepiece before today. However, the model will be delivered to Tiffany locations in New York, Beverly Hills, and San Francisco later this month, bringing fantasy to reality.

To commemorate the 170th anniversary of Patek Philippe’s partnership with Tiffany, this Nautilus will be limited to 170 pieces, including one that the retailer plans to consign to Phillips for its New York watch auction on Saturday, with proceeds benefiting The Nature Conservancy, a global environmental organisation.

On a video call in mid-November, Patek Phillipe’s president, Thierry Stern, said, “We’ve been workinOn a video call in mid-Novemberlest retailer in the United States,” says thesaid,p”We’ve been working so long with Tiffany.”mily when I was growing up, and I’m not just talking aTiffany,e business.”

Tiffany became the Swiss company’s first authorisefamily. dealer in 1851, and the two companies have been doback to usiness together since then. The agreement has survived numerous ownership changes over the years, including the Stern family’s purchase of the watchmaker in 1932 and LVMH Mot Hennessy Louis Vuitton’s $16.2 billion acquisition of Tiffany in January.

Mr. Stern said he wanted to tell Tiffany that “you have been doing a great job,” especially now that the sale to LVMH has been completed.

But, he added, “I’m not sure it’s a gift for them.” “It could be a major issue.” They might not realise how difficult selecting clients will be.”

That could be the year’s understatement. The frenzy over those 170 timepieces that is sure to erupt among longtime Patek Philippe collectors and important Tiffany clients will be almost unprecedented.

The Ref. 5711 has long been one of the industry’s most coveted wristwatches, having been introduced in 2006 as a refined version of the orig—itsselfaNautilus, a stainless steel luxury sport watch influenced by nautical motifs and designed by the celebrated Gerald Genta. Prices for pre-owned items began to rs around the time of the coronavirus pandemic. When Patek Philippe announced the model’s discontinuation earlier this year, the secondary market reacted by pricing it at nearly four times its retail value of $34,890.

Mr. Stern said in February that his decision to give the model “a victory lap” could provide hope to collectors who had signed up for waiting lists that were eight, even ten years long.

“The Ref. 5711 will have a surprise final series,” Mr. Stern said at the time. “And it’s not what was in the pipeline at the time.”

The Ref. 5711-1A-014, a highly sought-after olive refial version introduced in April and priced at $34,890, was on the winning lap. Three months later, at an Antiquorum auction in Monaco, one piece, still in its factory-sealed packaging, sold for 416,000 euros, or $466,625.

“I’m confident that a Tiffany-signed green dial would fetch $800,000,” said John Reardon, the founder of Collectability, a vintage Patek Philippe educational platform and online reseller. (Mr. Reardon was referring to retailer-signed dials in general, not the Tiffany Blue watch specifically.)

In the twentieth century, watchmakers such as Patek Philippe and Rolex honoured their relationships with retailers like Serpico y Laino in Caracas, Venezuela; Beyer in Zurich; and Freccero & Cia. in Montevideo, Uruguay, by stamping the names on the faces of their timepieces. Models, on the other hand, were not always in high demand.

Mr. Reardon said that “twenty years ago, I had a number of collectors refer to retailer signatures on a Patek Philippe dial as nothing more than graffiti.”

Collectors now value original conditionabove all else, he continued. Mr. Reardon explained, to the retailer’sind a beautiful dial with a retailer signature, it often indiates the dial is original and unrestored.” “These Patek Philippe iconic references with rtailer signatures are considered benchretailer’sphies.”

Tiffany-signed pieces have a special “magic,” according to M. Reardon, which may have something to do with Tiffany’s long-standing relationship with Patek Philippe. They tend to go to loyal collectors rather than opportunists looking for a quick buck.

“Everything has a price,” he explained, “but not for these collectors.” “To them, that Tiffany signature is sacred, priceless, and something to be passed down through the generations.”

The price of the new model will be $52,635. The higher price, according to a Patek Philippe spokeswoman, is priceless,e additional work involved in customising and producing a small costries.

Tiffany executives could not be reached for comment on the timepiece. (Mr. Stern said he spoke with Alexandre Arnault, Tiffany’s executive vice president of product and communications, about the limited edition. Bernard Arnault, his father, is the CEO of LVMH.) But it’s just the latest innovation since LVMH took over the house, joining the Supreme collaboration, the Beyoncé and Jay-Z ad campaign, and the house’s first-ever line of men’s engagement rings in raising the brand’s profile.

In addition to a commemorative inscriptioncampaign,sapphire crystal caseback that reads “170th Anniversary 1851-2021 Tiffany & Co. — Patek Philippe,” Mr. Stern alluded to another detail that may make the model, and the retailer, even more buzzworthy: the watch includes what moviemakers and software companies call an Easter egg.

“I’m interested to see how long it takes pe–ple to figure out.—t each piece has a secret,” Mr. Stern said.

He paused before responding with a remark that seemed to acknowledge the question that many in the watch industry might have when they heard about the limited edition: Is Patek Philippe for sale, and will Tiffany’s parent company be the buyer?

Mr. Stern said of the Easter egg, “It’s fun; it’s not commercial.” “That’s something only a family business can do.”