Often overlooked as it’s hidden by your wrist, the caseback is more than meets the eye. It can be solid and straight forward, decorative, adaptive for divers and even a window to the movement. Casebacks are literally the backdoors of a watch and almost always the access point for maintenance and repairs. The hands, dial and movement are also installed through the back during assembly (with very few exceptions), making the caseback a vault door for the watch's precious cargo. Let’s explore the different types and how they contribute to the overall look and function of a watch.
Snap-On
As the name implies, snap-on casebacks literally just snap into place via pressure and friction, no different than the battery cover on a remote. This simple, proven design allows for a thin profile and ease of use. Any watchmaker can easily remove one for servicing and it’s among the easiest for do-it-yourself hobbyists as well. Most vintage watches have snap-on backs along with many dress watches today, but there are drawbacks to the sleek and simple design. For starters, water resistance is compromised with this type, often limited to 30 meters or so. That’s rarely an issue for a proper dress watch, but field watches and other affordable options won’t be as robust as better equipped counterparts. Snap-ons are usually solid as well, meaning exhibition windows to view the movement are generally unavailable.
Screw-Down
Screw-down backs thread onto the case for a more secure enclosure. This is necessary for meaningful water resistance and almost all dive watches have this type of caseback. Working in tandem with an o-ring or comparable gasket, screw-down backs create a very strong seal that allows for well over 100 meters of water resistance. There are various designs, including exhibition backs, but all ultimately thread onto the case. Removing them depends on the design, which can include notches, special knurling and so on. Our Supersede Date, for example, has a screw-down caseback with a sapphire exhibition window, allowing for 200 meters of water resistance.
Screw-On
Unlike screw-down casebacks, screw-on ones use actual screws to secure the back in place. Multiple screws will be clearly visible and can be as few as four and as many as eight or more. This allows for a tight seal as well, so water resistance ratings can also be high with screw-on backs. The UTS 1000M V2 dive watch, for example, has a staggering 1,000 meter water resistance rating with a screw-on caseback. Although similar in function to their screw-down counterparts, screw-on casebacks tend to be easier to remove.
Exhibition
Exhibition casebacks aren’t limited to a specific type (as seen above), but are generally not seen on snap-on backs as mentioned. They used to be avoided by divers for compromising water resistance, but that’s no longer the case today. Serious saturation dive watches often have exhibition backs to show off the movement. These windows to the heart of a watch can be sapphire, mineral glass and even acrylic, depending on the application and price points. Sapphire is the most scratch resistant, while acrylic is generally shatter-proof. Mineral glass falls in the middle with reasonable scratch resistance and adequate strength for serious water resistance. Exhibition casebacks are usually reserved for mechanical watches, but can occasionally be found on quartz pieces from Grand Seiko, Citizen and more.
At Horage, we design and engineer all movements in-house, so we’re proud to display them through the caseback. All of our exhibition windows are sapphire and although there's not a dedicated diver in the portfolio, the Supersede GMT and Date models have diving bezels and 200 meters of water resistance. This is adequate for all recreational diving and only deep saturation divers would need more.
Super Compressor
There’s a diving-specific type of caseback developed in the 1950s (patented by EPSA in 1956) called a super compressor. Water pressure compresses the back as a diver descends, increasing water resistance. Usually spring loaded, the caseback literally tightens against the gasket for maximum protection, but loosens a bit when out of water. At the time, this provided some of the best water resistance available, while otherwise keeping pressure off of the gasket to increase longevity. These are most recognizable by the case having two crowns - one at 2 o’clock to rotate an internal bezel and one at 4 o’clock to wind the movement and set the time. Not all super compressor watches are designed like this, but the majority are.
Conventional designs have surpassed the advantages of super compressors today (which were phasing out by the 1970s), but they’re still being produced by a handful of brands for both novelty and historical interest. Farer’s Endeavour series is an example of a modern super compressor at an affordable price.
Custom Engravings
Some backs are deliberately left blank for custom engravings. Fine watches can be very expensive by any standard, making them ideal gifts for major anniversaries, birthdays, job achievements and so on. Personal engravings are a perfect touch and can greatly enhance the sentimental value. On the other hand, custom engravings can negatively affect the value on the resale market. Many scoff at messages or dated events from strangers on the back of an expensive watch. What means a lot to one can be a bit of an eyesore to another.
That said, personal engravings can also increase the value of a watch if there’s historical significance. Was it owned by a former president or legendary singer? Was a caseback hastily engraved in the trenches during World War II? And so on. Custom engravings are a historic part of watchmaking and reflect the history of families, relationships, job achievements and much more.
Decorated
In lieu of an exhibition caseback, many are intricately engraved with images or patterns to reflect the model, series or brand. This tends to be most common with dive watches that opt for solid backs to keep serious water resistance more economical. For example, Certina’s DS Super PH1000M has a detailed engraving of a sea turtle, while Edox’s Neptunian Grande Reserve has an engraved image of King Neptune, the Rome god of the sea.
Hinged
Hinged casebacks are a rarity today and generally go back to the era of pocket watches (known as hunter or double hunter pocket watches with lids over the dial and movement). It’s unthinkable today, but there was a time when the back would simply open on a hinge and fully expose the movement. This made adjustments and maintenance easy, but also allowed dust, moisture and so on to intrude.
A small handful of watches today have hinged backs, but as far as I know, all have protective sapphire or glass “second” backs to protect the movement and maintain water resistance. This is generally reserved for very expensive, high-end pieces like Patek Philippe’s Calatrava Ref. 5227G, but more affordable options exist like Alpina’s Startimer Pilot Heritage. There are also affordable double hunter pocket watches with contemporary glass “second” backs to enjoy the past without exposing the movement.
This doesn’t cover every possible type of caseback, but does hit on the most common. At Horage, we like to celebrate our in-house movements that include the K1 automatic, K2 micro-rotor, K-TOU tourbillon and K-TMR micro-rotor tourbillon. So, we opt for sapphire exhibition casebacks to display our industry-leading mechanical marvels. However, personalized engravings and special serial numbers are still possible on the perimeter steel, gold or titanium (depending on the case), so customization isn’t off the table. As a performance watchmaker, we focus on every aspect of the watch, from the hands, dial and case to the movement, bracelet and even deployant clasp like our 5.6mm ultra-thin micro-adjusting clasp (HMAC).
We Want to Hear From You!
Sound off in the comments about additional topics of interest, so we can be sure to cover what you want to read in future articles. And please share this with friends and anyone interested in watchmaking, and let's keep the conversation going. Also, be sure to sign up for our newsletter (here) and keep an eye out for new products as we're always in the process of development. Check out journal entries as well (here) and a detailed section on performance watchmaking at Horage (here).
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Erik Slaven
Horage does some stellar casebacks - large sapphire glass and and beautiful movement decoration.
Couple questions:
How are horage screw down casebacks removed without indents for a tool? As a hobbyist, I've removed the caseback from some inexpensive watches to understand them better. While I wouldn't try this with a Horage, I was mystified how a tight screw down caseback is removed without ability to accept a tool.
Box crystals seem to add more light to dials, as it's able to enter from the side. I'm curious of any watches that have expored using box shape crystal for exhibition caseback. Perhaps curved, to better fit the wrist? For a tourbillon watch it might better highlight the beautiful complexity when viewed from the front? Yes, light would be minimal and case slightly thicker (your watches are all so thin, they could afford an extra mm). But, as opposed to sapphire cases or case side windows, it's a low cost, low effort trick to accomplish a similar result (maybe? I've no if it'd work!).