Ever since it was discovered that combining iron, chromium and carbon made a material that could be used to make almost anything, stainless steel has been king of construction. It’s strong, it’s malleable, its hardy—and that’s why it’s also used for making watches. What more could you ask than that? Well, apparently you can get watches made of other, more exotic materials as well. But why?

The Luminor has been a staple of Panerai’s collection since the Italian company first opened its doors to the public in 1993, this Base the purest and simplest iteration. It’s been discontinued now—and cost around £4,000 before it was—by something that looks exactly the same but costs over £1,000 more. Why would anyone want to pay that?

You could be forgiven for thinking the watch I'm holding right now is a fake. After all, it says 'Panerai' on it, yet looks nothing like the Radiomir or Luminor shapes the brand has become famous for. I can assure you, however, that this is a legitimate Panerai model, and not just any Panerai model—the Panerai Mare Nostrum is one of the most mysterious Panerai has ever made.

In 1936, dive gauge manufacturer Officine Panerai and watchmaker Rolex joined forces to build a watch at the request of the Italian Royal Navy. Intended for use during covert, night-time dives, Panerai's expertise gave what was essentially a complete watch from Rolex that extra level of functionality: a glowing dial. With numerals that shone clear and legible at a consistent and unfaltering rate, the Panerai watch was unstoppable. There was just one tiny problem with it, however—that glowing dial was deadly.