How to Build a Seiko Mod Nautilus-style Open Heart
Sometimes watch brands are so proud of their movements that showing it off through a display caseback is not enough - they want to show off the front of the mechanism as well. And who can blame them, really? Watch calibers are such intricate pieces of machinery that they become feats of design and engineering, and it can be a shame to just hide it away inside a stainless steel case.
Source: Seiko Boutique
That’s when open heart/openworked watches came to be. As the name suggests, this watch will have holes in the dial, and in some cases even remove it entirely, so the watch wearer can directly look into the watch’s heart or movement. It can be a divisive feature, but all can agree that it makes for a more unique look and adds a premium feel to a watch build.
A certain mod that’s popularly compatible with open hearts is the Seiko-naut build, which is a combination of a Seiko and Patek Philippe’s Nautilus. The luxury-inspired case lends well to the aesthetic of an open dial, creating a stunning balance between rugged functionality and refined elegance. This fusion of styles allows for a unique timepiece that stands out, offering the sophistication of a high-end watch with the versatility of a customizable mod.
In this article, you’ll know more about open heart watches, some models to take inspiration from, and what parts you’ll need to build an open heart Seiko-Naut build.
History and Consumer Opinions
Open heart watches are not entirely new, with evidence of its inception having been introduced in the late 1970s. Revue allegedly pioneered the concept in 1979, showcasing hand-finished movements through a small aperture. We say allegedly, as there are not many online resources to support this information.
Source: Europa Star
The design evolved, with Frederique Constant popularizing the term "Heart Beat" in 1994, sparking widespread adoption and copycatting across the industry, apparently due to FC’s failed patenting attempt. Watch historians would argue though, that FC only coined the term, while the design itself has been around for much longer.
This unique design feature offers a mesmerizing glimpse into the watch's soul, revealing the intricate dance of the escapement – the timepiece's beating heart. The circular opening, typically positioned between 6 and 10 o'clock, exposes the balance wheel and anchor, the most dynamic parts of the movement.
Sentiments about open heart designs are mixed. Many watch fans appreciate the blend of engineering and artistry, viewing these timepieces as miniature works of art. Others find them distracting or overly busy. Some critics argue that they can appear gimmicky, especially when featuring basic movements. Despite divided opinions, open heart watches continue to fascinate and intrigue, offering a unique mix of form and function in the world of horology.
Watches for Inspiration
Presage “Style60’s” Series Open-Heart White Ref. SARY189
Source: @ryubo_watchsalon on IG
The Seiko Presage SARY189 "Style60's" Open Heart beautifully combines vintage aesthetics with modern watchmaking. This timepiece pays homage to Seiko's 1964 Crown Chronograph while incorporating contemporary elements that appeal to today's watch enthusiasts.
The 40.8mm stainless steel case strikes a perfect balance between dressy and sporty, making it a good daily driver, plus it has a slim 12.8mm profile and 47mm lug-to-lug distance to ensure comfort on most wrists. The silvery-white dial features sharp dauphine hands and applied hour indexes, evoking the timeless charm of its predecessor. It is powered by Seiko's reliable 4R39 automatic movement, visible through the exhibition caseback, giving the SARY189 offers a 41-hour power reserve and 50m water resistance.
The watch's standout feature is the 9 o'clock cutout, offering a glimpse into the movement. Complemented by a 24-hour subdial, this design adds depth and intrigue to the dial. The domed Hardlex crystal further enhances the vintage appeal while providing a good amount of durability.
Hamilton Jazzmaster Open Heart Lady Auto
Source: @hfagetakasaki on IG
Like the SARY189, the Hamilton Jazzmaster Open Heart’s signature feature is the openworked dial, with a series of carefully placed cutouts that let you catch glimpses of the intricate mechanisms at work. Unlike a simple circular hole that usually only shows the escapement, the dial design is carefully planned to show multiple aspects of its H-10 movement.
Aside from the cutout, the dial colors are equally striking, with deep blues, rich greens, and sleek silver-whites. Some versions even feature a gradient effect, adding visual depth. The sapphire crystal, which is scratch-resistant, adds a premium touch and provides a clear view of its pièce de résistance.
Available in both 40mm and 36mm sizes, this model caters to different wrist sizes and style preferences and is built with a sturdy 316L stainless steel case. The case's finish is thoughtfully executed, with a mix of satin-brushed and polished surfaces that catch the light at different angles, adding dimension to the overall look.
Building a Seiko-naut Mod with an Open Heart
Why a Seiko-naut, you might be asking? While the open heart dial can be used with any dress watch build, it’s quite common to see it being used with a Nautilus-inspired case. This may be a bit of a head-scratcher as Patek Philippe is not really known for this particular design trend, although they do have a Skeleton watch entry with the Calatrava. We’re not complaining though, as the design fits the aesthetic of the case just fine, which might be why there are a lot of searches for guides on how to make one of these.
Source: @mdratelier on IG
The main thing to note is that most aftermarket openworked dials will only have the open part on the 9 o’clock marker. This is due to the fact that there is only one suitable movement for this type of mod, which is the skeleton NH70/71/72. Other Seiko modding movements like the commonly used NH35/36 do not have any notable design features on the dial side, so it is a must to use the Skeleton NH series instead which has a gold escapement.
Once you have your Skeleton NH and your open heart dial, you’ll just need to choose which finish you want your Nautilus-style case in. We have the NMK926 which has a rehaut chapter ring (one less thing for you to worry about), or the NMK935 which has an interchangeable chapter ring if you want more flexibility. Both versions are available in Stainless Steel, PVD Black, Rose Gold, and Two-tone finishes. Wrap it up with these Nautilus hands and you’ve got yourself an Open Heart Seiko-Naut watch!
Wrap Up
Open heart designs bring flair to Seiko mods, offering a direct view into the watch's beating mechanical heart. These eye-catching modifications are pretty easy to incorporate, allowing even novice modders to create stunning timepieces.
Don't forget to explore our extensive selection of Seiko mod parts to find the perfect components for your next project. Whether you're aiming for a classic look or a bold statement piece with modern features, we have the parts for you.
Happy modding!