On Monday, Christie’s announced that it’ll be selling Rolex Deep Sea Special No. 1 at its November Geneva auction.

Deep Sea Special No. 1 is, well, the first Rolex Deep Sea Special Prototype made. Rolex attached it to Auguste Piccard’s bathyscape Trieste in 1953 when it dove 3,000 meters deep into the Mediterranean as a bit of a marketing stunt to prove that, why yes, we do make the very best dive watches around. It’s believed that Rolex produced seven Deep Sea Special Prototypes, and 3 have been found. Deep Sea Special No. 3 made the trip to the bottom of the Mariana Trench on Trieste in 1960, James Cameron style, and now sits at the Smithsonian. Finally, Deep Sea Special No. 5 was last seen at Christie’s in 2000.

Of course, to call it a “marketing stunt” is a bit of an unfair characterization. The Trieste was a research bathyscaphe developed to achieve the goal of reaching the deepest known point of the oceans, the bottom of the Mariana Trench. It was the deep-diving version of putting a man on the moon, just to prove we could. Rolex hopped on board to see if it could test itself as well, developing watch technology that could survive these same depths. Really, it’s fascinating they were developing this in parallel with the Submariner ref. 6204 (also released in 1953), and seeing how different the final products are.

Christie’s previously sold Deep Sea Special No. 1 in 2005 for CHF 322.4k. As Hodinkee later revealed to us in a Talking Watches, it was purchased by collector Reza Ali Rashidian and has sat proudly as the keystone of his serious Rolex dive watch collection since then. In that Talking Watches episode, Mr. Rashidian mentions it would’ve been the world-record price for a Rolex at the time, so it’s wild to think about how far Rolex and watch collecting have come since. Now, have a scroll and you’ll see your friendly neighborhood Chrono24 dealers have at least a few pages worth of Rolexes with asking prices above $300k.

Let’s be honest, it’s a well-timed coup by Christie’s. The announcement comes just a week after Phillips announced that it would also be offering a Deep Sea Special at its Geneva auction.

But the Phillips Deep Sea Special was produced after these Deep Sea Special Prototypes.

After Deep Sea Special No. 3 made it to the bottom of the Mariana Trench, Rolex produced about three dozen display models of the Deep Sea Special to celebrate and commemorate the achievement. The Deep Sea Special offered by Phillips is Number 35 of that commemorative series.

Christie’s also made the last public sale of one of these watches, selling Number 31 for HKD 3.3m in 2009.

So if you’re keeping track, Deep Sea Special No. 3 (the one that went to the Mariana Trench) is perhaps the most desirable of the Deep Sea Specials, but since you’d have to complete a Nicholas Cage National Treasure-level heist to boost that from the Smithsonian, the Christie’s Deep Sea Special No. 1 is the most important Deep Sea you’ll have the opportunity to get your hands on.

Christie’s hasn’t given an estimate for Deep Sea Special No. 3 yet. Meanwhile, Phillips placed an estimate of CHF 1.2m-2.4m on its commemorative series example. But really, it’s anyone’s guess how these two lots might fare. It kind of reminds me of the spring season, when two rare Cartier Pebbles popped up out of nowhere, both doing big numbers. Could both Deep Sea Specials get big results too?

Perhaps it’s worth noting that the commemorative series example from Phillips will be offered a day before the Christie’s sale of Deep Sea Special No. 1. Is it possible bidders will be sitting on their paddles, waiting for the rarer of the two at Christie’s the following day? Or, might people figure that big institutional money is going after Deep Sea Special No. 1, and bid all their ducats on the Phillips lot instead?

More to come.