Serica Bolsters the 5303 COSC Antimagnetic Diving Chronometer from Within

Although Serica has only been around since 2019, it feels like the young watch brand has been around for ages. In my opinion, a lot of that has to do with the maturity in which they conduct themselves, both in brand presence and progression. With any Serica novelty, you can bet that their approach to any watch design is performed with metronomic consistency – typically with minimal branding, steady visual cues, and a general inspiration by way of vintage military timepieces. It seems that any change that’s going to be made within each reference will be incremental, but that doesn’t mean the impact can be monumental. Such is the case with the new and improved Serica 5303 COSC Antimagnetic Diver Chronometer.

To understand the latest update to the Serica 5303, we must look within. Serica has opted to keep the movement within the Soprod family, but instead of using the previous Newton P092 automatic, the Serica 5303 COSC now draws its power from the Caliber M100. The Soprod Caliber M100 is buoyed by a glucydur balance, incabloc shock system, a 42 hour power reserve, and most importantly, a 3.2mm movement thickness. With approximately 1.4mm of extra room to play using the transitional movement inside of the 5303 COSC case, Serica has built in several antimagnetic pieces including a soft iron movement holder, soft iron dial and a soft iron inner caseback. As a result, the magnetic resistance for the Serica 5303 COSC diver has skyrocketed from the traditional Swiss standard magnetic resistance rating of 4,800 A/m to a sizable 50,000 A/m.


I’m sure the obvious has already been stated, the Serica 5303 refresh comes with the respectable COSC certification, ensuring that each chronometer has a unique COSC engraved number on the movement, and has gone through a battery of tests while maintaining consistent accuracy performance. But in addition to the COSC certification, Serica is also making sure that the movement is up to snuff by performing its own in-house testing. From here on out, any watch provided by Serica will also come with their Grand Chronomètre credential, which assures the buyer that once the watch is fully assembled, it will then undergo additional accuracy, power reserve and shock resistance testing.

To the eye, the exterior of the Serica 5303 COSC diver remains entirely the same (well, almost). Once again, Serica’s calling card of design consistency is on full-display. The dial continues to use their peculiar hour marker arrangement – Super-Luminova C3 filled rectangular bars at the cardinal hours and lollipop markers that extend towards the center of the dial. Like all the models in the Serica catalog, a broad minute and hour handset dances around the dial (also filled with Super-Luminova C3). The only subtle difference is that the S617 word-marking is no longer displayed and is replaced by the Chronomètre tag. For those who are curious, the S617 name refers to a retired French submarine called the e téméraire (the brave one). Although the S617 moniker no longer remains as part of the 5303 name, the watch still remains as Serica’s distinct flagship diver, and continues to pay tribute to their vintage military inspiration.

One of my favorite features of any Serica piece is the ability to choose the crown placement of your liking, whether that be at three o’clock, or if you’re feeling zesty (or you’re an actual lefty), elect to go with a crown at nine o’clock. The case lines are highlighted by varying uses of finishes and hits all the sweet spots in regards to proportions – 39mm in width, 46.5mm in lug to lug and 12.2mm in thickness. The MVP of the entire package however just so happens to be their steel mesh bracelet. The Serica 5303 COSC retains the 20mm solid end-link design that houses an additional articulating link, which then transitions into a silky smooth steel mesh bracelet that tapers to 16mm at the clasp.

These small changes continue to add up and make an already solid, distinct diver that much better. Serica has doubled-down on themselves in regards movement quality, and has most certainly put to bed any movement concerns moving forward. Throw in the added magnetic resistance, especially with the increasing amount of surrounding magnetic fields from day to day objects, it just makes the case stronger to own a Serica 5303 as an everyday diver. The 5303 remains as my leading favorite out of their entire catalog. Yes, it positions higher above their 8315 GMT Chronomètre. I’m one hundred percent all in with the dual-function bezel display. With one easy turn of the bezel, you can track a second time zone, which at the moment, just sounds way more convenient then fiddling with a crown to adjust a second hour hand. The graduated elapsed time bezel with a 15 minute countdown, now using a ceramic insert, is the cherry on top. There are a few brands out there that I constantly ask myself, “Why don’t I own anything from them?” Serica remains as one of those brands, and I think I should change that very soon.

Serica is offering the 5303 COSC Antimagnetic Diver Chronometer in all three color variations – Enamel Black, Porcelain White, and Crystal Blue. With the notable upgrades, the Serica 5303 COSC Antimagnetic Diver Chronometer sees a slight bump up in price to $1,635 including VAT (~ $300 more than the original pricing of the first 5303 diver). A small premium, but there’s no doubt that you’re getting into a better watch all around … one that won’t look like your ordinary diver in, and out of the water, and that my friends, is a good thing. Serica

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Thomas is a budding writer and an avid photographer by way of San Diego, California. From his local surf break to mountain peaks and occasionally traveling to destinations off the beaten path, he is always searching for his next adventure, with a watch on wrist, and a camera in hand. Thomas is a watch enthusiast through and through; having a strong passion for their breadth of design, historical connection, and the stories that lie within each timepiece.