Seiko 6105-8000 vs 6105-8110: What’s the Difference?

There are watches you notice because they are beautiful. There are watches you notice because they are expensive.

And then there are watches that, for reasons that are sometimes difficult to explain, simply feel right.

The Seiko 6105 is one of those watches.

Ask most vintage-watch collectors to picture a 6105 and they will probably see the large, asymmetric case of the 6105-8110. They may know it as the “Willard,” remember Martin Sheen wearing one in Apocalypse Now, or simply recognise that unmistakable crown guard and cushion-shaped case. But before the Willard became the watch we all know, there was another 6105. Smaller. Simpler. More restrained. The 6105-8000. And if you have spent enough time looking at vintage Seiko, you eventually realise that the less famous watch may actually be the more interesting one.

The beginning of the 6105 story

Seiko’s first serious dive watch was the 62MAS, introduced in 1965. By the end of the decade, Seiko was already developing the next generation of divers. In 1968 came the 6105-8000. At first glance, it doesn’t look radically different from the divers that came before it. It has the familiar black dial, luminous markers, rotating bezel and a crown positioned at four o’clock. But look closer. The case is completely its own thing.

The 6105-8000 has a relatively compact, symmetrical cushion shaped case, measuring around 41mm across. The crown sits neatly at four o’clock, partially recessed into the case, giving the watch a clean and purposeful appearance.

It is a surprisingly elegant piece of industrial design. And, importantly, this is where Seiko’s now familiar four o’clock diver crown really begins to take shape. Contemporary Seiko material described the recessed crown as “anti-snag” a wonderfully practical description for a watch designed to be used rather than admired in a display cabinet.

The 6105-8000 was rated to 150 metres and used Seiko’s automatic 6105 movement. Early examples used the 6105A, with later examples incorporating the 6105B. Both are 17-jewel automatic movements operating at 21,600 vibrations per hour. It was, in other words, a serious watch. Just not yet a famous one.

Then Seiko changed everything. Around 1970, Seiko introduced the 6105-8110. The name remained almost the same.

The watch did not. The most obvious change is the case. Where the 8000 is symmetrical and relatively compact, the 8110 has a much larger, unmistakably asymmetric cushion case. The crown is still at four o’clock, but it is now protected by an integrated crown guard that flows dramatically into the case. It is a fantastic piece of design. It also looks enormous compared with the 8000. The 8110 is roughly 44mm across, compared with approximately 41mm for the 8000. On paper that doesn’t sound like much, but on the wrist the difference is immediately apparent. The 8000 feels comparatively slim and understated. The 8110 has presence.

And then there is the crown. Rather than simply sitting recessed into the case, the 8110 introduced Seiko’s distinctive turn-and-lock crown system. It isn’t a conventional screw-down crown; instead, the crown is secured through a clever locking arrangement integrated into the case. It’s one of those wonderfully peculiar Seiko solutions that makes you wonder how anyone ever thought of it.

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8000 vs 8110: The important differences. So, what actually changed?                    

The 8110 also brought the 6105B movement into the picture, with hacking capability. Both generations retained Seiko’s Magic Lever automatic winding system and did not have manual winding. There are, however, numerous small specification changes throughout the production of the 6105 family. This is where things become particularly interesting for collectors.

The “Water Proof” question. If you spend any time looking at vintage 6105s, you’ll eventually encounter the terms:

Proof/Proof. Proof/Resist. Resist/Resist. These descriptions refer to the wording found on the dial and case back as Seiko transitioned from the older “Water Proof” terminology to “Water Resist.” The 6105-8000 family therefore isn’t as simple as looking at a photograph and assigning one specification to every watch carrying the 8000 reference.

This is one of the reasons I always encourage collectors to look at the entire watch, rather than simply matching a reference number to an image found online. The dial, case back, movement, crown, bezel and case should all make sense together. That matters enormously with vintage Seiko.

So which one is better? This is where things get subjective. If you want the most recognisable watch, the 6105-8110 wins. There is no argument. The asymmetric case is one of the defining designs in Seiko’s history. It eventually became the foundation for the 6306 and 6309 “Turtle” family, and its appearance in Apocalypse Now turned the 8110 into something far beyond a Japanese dive watch.

But if you ask me which one I find more fascinating, the answer is less obvious. I have a soft spot for the 6105-8000.

Perhaps it’s because it is the less obvious choice. Perhaps it’s because the case is so clean. Or perhaps it’s because, after decades of watches becoming larger and more complicated, there is something refreshing about a 41mm Japanese dive watch from 1968 that simply gets on with the job. The 8000 feels like a tool. A very well-designed tool.

And there is something wonderfully honest about that.

The rarity of the 6105-8000. There is another reason collectors have started paying closer attention to the 8000.

They are simply harder to find. The 6105-8110 was produced for several years and became enormously popular with collectors. Consequently, examples appear relatively regularly on the vintage market. The 8000 is a different story.

It had the shorter production run, is older, and has not enjoyed the same level of fame. Good, original examples are considerably less common. And that last word is important, Original. Finding a 6105-8000 isn’t particularly difficult.

Finding a genuinely good one is. Finding one with its original dial, original hands, correct bezel, correct crown, sharp case and honest ageing is another matter entirely. That is where the real collecting begins.

Patina is part of the story

One of the things I love about vintage watches is that they don’t all need to look new. In fact, I think many of them look worse when they do. A 1968 Seiko 6105 should look like a 1968 Seiko 6105. The case may have marks. The dial may have aged. The luminous material may have changed colour. The bracelet may have seen better days. Those things aren’t necessarily faults. They are evidence that the watch has lived a life. Of course, there is a difference between attractive ageing and deterioration. Corrosion, damaged components, moisture ingress and poorly executed repairs are very different things from honest patina. The challenge is knowing the difference. And that is one of the reasons buying an original vintage watch can be so rewarding.