As Arthur C. Clarke wrote at the beginning of his epic novel of first contact, Rendezvous With Rama, “sooner or later, it was bound to happen.” So it is with the replacement of the caliber 1861 Moonwatch, with a new version, using the co-axial caliber 3861. Omega announced an upgraded version of the caliber 1861 in March of 2019 – the new version, the Omega Speedmaster Professional Moonwatch 3861, first appeared in the gold-on-gold Apollo 11 Anniversary Limited Edition. Since then, it’s appeared in two more watches – in May of 2019, in the Apollo 11 50th Anniversary Limited Edition, in stainless steel; and then, in October of 2020, in the “Silver Snoopy” 50th Anniversary Speedmaster (the model has proven to be extremely popular and, despite the fact that it is not a limited edition, extremely difficult to get).

Today Omega’s finally announced what we all pretty much knew to be inevitable: a standard-production Moonwatch, but with the co-axial escapement equipped, Master Chronometer-certified Omega Speedmaster Professional Moonwatch 3861. The caliber 1861 is now officially discontinued, marking the final retirement of what had until now been the most recent heir to the original caliber 321, after a production run in the Speedmaster Professional Moonwatch of fifty or so years (the calibers 861/1861 began to replace the 321 in 1968/69).

The new Omega Speedmaster Professional Moonwatch 3861 is, in every respect, still the Moonwatch. Some of this is simply a matter of not interfering with a design which has become one of the great icons of modern watchmaking, and some of it is pragmatic. Omega obviously wants the 3861 Moonwatch to continue in the tradition of flight-qualified Omegas, and the new 3861 Moonwatch is, thanks to its continued adherence to the configuration flight-qualified by NASA, also certified for use in manned space flight. It also remains the only flight-qualified watch suitable for EVA – quartz watches, especially with LCD displays, are very vulnerable to temperature changes, and the fact that LCDs can be destroyed by temperatures routinely encountered during spacewalks has continued to make the Moonwatch – both with the 1861 and now, the 3861 – a useful watch in the brutal environment of interplanetary space as well. Along with the new movement, the latest version of the Moonwatch also gets a new bracelet – there are five links per row, and each link is smaller than in the previous bracelet and it looks as if it should wear lighter and more comfortably as well. The bracelet is one of the places in which you can see small differences between the Hesalite and sapphire models – on the sapphire model, the intermediate links are mirror polished, however they’re matte-finish on the Hesalite model.

We’ve said that you would be hard-pressed to tell the difference between the 1861 Moonwatch, and the 3861 Moonwatch, but the truth is, I think a lot of us would be hard-pressed to tell the difference between the 1861 and the 3861 too. The two movements are at first glance (and maybe second or even third) virtually identical. Both use the same lever and cam switching system for the chronograph which was first introduced in the transition from the 321 to the 861, and the general layout of the plates, bridges, jewels, and other components is virtually identical from the 1861 to the 3861. Functionally speaking, one difference owners will notice right away is that the caliber 3861 has a stop seconds (hacking) feature; the first Moonwatch caliber to do so. The new Omega Speedmaster Professional Moonwatch 3861 also features design elements from the vintage ref. ST 105.012, including the dot-over-90 bezel, and step dial. One of the notable differences, however, is in the configuration of the balance spring. The caliber 1861 uses a fairly standard regulator sweep, which controls the effective length of the flat Nivarox-type balance spring, and which is used for fine regulation of the watch. A closer examination of the caliber 3861 reveals that there’s no such regulator – instead, the 3861 uses a freesprung, adjustable mass balance with a silicon balance spring, which allows the new Moonwatch to run within the Master Chronometer specification of 0/+5 seconds per day (this is the official spec but I’ve yet to have a Master Chronometer/METAS-rated watch in for review which did not keep a notably much closer rate – they seem to wander back and forth around a half a second more or less per week, under real-world conditions).

That co-axial escapement, and the silicon balance spring, make for a movement which is in fact far better suited to the rigors of spaceflight than the 1861. The 1861’s service record in space considerably surpasses that of any other mechanical movement, but it simply can’t compete functionally with the 3861, which can resist magnetic fields up to at least 15,000 gauss and which should be able to better resist shock, temperature changes, and keep a closer rate over a longer time period as well (and, of course, which also enjoys an advantage over the 1861 in terms of service interval as well).

One fairly big unanswered question is whether or not the new movement has been run through the battery of tests NASA required for the original 321 Speedmaster. We’re hoping to reach out to Omega for clarification on this, but given the fact that the Omega Speedmaster Professional Moonwatch 3861 is basically a more robust version of the 1861, I can’t imagine that it wouldn’t be able to meet or exceed the robustness of the earlier movement. It’s worth noting, however, that the production version of the 3861 Speedmaster Hesalite model says, “Flight Qualified By NASA in 1965 For All Manned Space Missions” rather than the “Flight Qualified By NASA For All Manned Space Missions” of the 1861-equipped Moonwatch.

Other than that, the movements are kissing cousins. The power reserve goes up marginally in the 3861, from 48 to 50 hours, and the jewel count takes a big jump as well, from 18 jewels in the 1861 to 26 in the 3861 (one of these days, I’m going to sit down and figure out where all those extra jewels ended up). But the overall look and feel between the two is very close – the Omega Speedmaster Professional Moonwatch 3861 really does feel like a logical next step in the evolution of the original caliber 321, not a dramatically disruptive break with its predecessor.