# Orient AC0Q Diver II vs. Seiko Prospex SPB177: What Does an Extra $530 Buy?

> The Seiko brings a 70-hour movement and a diver's rating for air diving. The Orient matches its accuracy rating in a far smaller case, and costs $530 less.

URL: https://wristmetric.com/comparisons/orient-ac0q-diver-ii-vs-seiko-prospex-spb177
Section: Comparisons
Published: September 13, 2026 (updated October 6, 2026)
By: Wristmetric Staff
Brands: Orient, Seiko

**The short answer.** The [Seiko](https://wristmetric.com/brands/seiko) Prospex SPB177 is the better [dive watch](https://wristmetric.com/dive-watches/). Its 6R35 runs for about 70 hours against the [Orient](https://wristmetric.com/brands/orient)'s 40, and Seiko rates it as a diver's watch for air diving. But the Orient AC0Q Diver II carries the same +25/−15 seconds a day accuracy rating, a sapphire crystal and a far smaller case, and at $370 it costs $530 less. For anyone who does not dive, that makes it the better buy.

| | Orient AC0Q Diver II | Seiko Prospex SPB177 |
|---|---|---|
| Price (US) | $370 (edge) | $900 |
| Reference | RA-AC0Q13E30B | SPB177 |
| Movement | Orient F6722, automatic | Seiko 6R35, automatic (edge) |
| Power reserve | About 40 hours | About 70 hours (edge) |
| Rated accuracy | +25/−15 sec/day | +25/−15 sec/day |
| Hacking | Yes | Yes |
| Hand-winding | Yes | Yes |
| Jewels | 22 | 24 |
| Beat rate | 21,600 vph | 21,600 vph |
| Case diameter | 39.9mm (edge) | 45mm |
| Thickness | 12.8mm | 12.9mm |
| Lug to lug | 46.5mm (edge) | 52.6mm |
| Lug width | 20mm | 20mm |
| Crystal | Flat sapphire | Sapphire with magnifier (cyclops) |
| Caseback | Solid, screw-down | Screw-down (not listed as see-through) |
| Water resistance | 200m | 200m diver's (air diving) (edge) |
| Bezel | Unidirectional, 120 clicks, stainless steel bezel | Unidirectional rotating, green to match the dial |
| Crown | Screw-down | At 4 o'clock |
| Lume | Luminous hands and hour markers | LumiBrite on hands and indices |
| Bracelet / strap | 316L stainless steel bracelet, fold-over clasp with diver's safety | Stainless steel bracelet, three-fold clasp with secure lock and extender (edge) |
| Warranty | 3 years (Orient Watch USA) | 3 years (Seiko USA, purchases on or after July 1, 2024) |

## Price

The AC0Q Diver II, reference RA-AC0Q13E30B, is $370 at [Orient Watch USA](https://www.orientwatchusa.com/products/ra-ac0q13e30b).

Seiko lists the Prospex SPB177 at $900 on its US site. That was also its launch price in 2020, according to Worn & Wound. But Seiko USA's online store no longer carries it, so it looks like a model on its way out, and buyers may need an authorized dealer.

At these prices, the Seiko costs $530 more, or a little under two and a half times the Orient's price.

## Design

The AC0Q Diver II is one of Orient's newest divers. Orient's global site dates it to March 2026, and Orient Watch USA describes it as a "complete dial redesign" with color gradients. The reference here has a green gradient dial. Orient's global site files the AC0Q range under the name "Diver Design 40," which describes a style and a size, not a rating.

The SPB177 belongs to Seiko's Prospex Sea collection. It was one of three US-exclusive "Ice Diver" models released in 2020, alongside the gray SPB175 and the light blue SPB179. Worn & Wound describes the case as "sumo-style." The bezel matches the green dial, and the crown sits at 4 o'clock.

The Seiko has the bolder case and the clearer story. The Orient is the more compact and restrained design. Taste decides this round.

## Movement

The Orient uses the F6722, made in Akita Prefecture by Akita Epson. It has 22 jewels, beats at 21,600 vph and runs for about 40 hours, with hacking, hand-winding and a date.

The Seiko uses the 6R35, with 24 jewels, the same 21,600 vph and about 70 hours of reserve. It also hacks, hand-winds and shows the date.

The reserve is the real difference. Seventy hours is nearly three days, enough for a watch taken off on Friday evening to still be running on Monday morning. Forty hours is not.

The Seiko takes Best Movement. For more on Orient's calibers, see [our explainer on Orient's in-house movements](https://wristmetric.com/culture/inside-orients-in-house-mechanical-movements).

## Case and Dimensions

The Orient measures 39.9mm across, 12.8mm thick and 46.5mm lug to lug, with 20mm lugs. It has a screw-down crown and a solid screw-down caseback. Orient's global site lists its weight as 165g on the bracelet.

The Seiko measures 45mm across, 12.9mm thick and 52.6mm lug to lug, also with 20mm lugs. Seiko lists a screw-down caseback. The crown sits at 4 o'clock, but Seiko does not say whether it screws down.

The thickness is effectively identical. The Seiko is 5.1mm wider and 6.1mm longer from lug tip to lug tip, a large gap between two dive watches.

## Dial

Orient describes the Diver II's dial as a green gradient, with luminous hands and hour markers and a date. It gives few other details.

The Seiko's green dial has a waffle texture, with LumiBrite on the hands and indices and a date under a magnifier.

On the published evidence, the Seiko has the more detailed dial and a magnified date. Buyers who dislike magnifiers will prefer the Orient. This round is close.

## Crystal

Both watches use sapphire. The Orient's is flat, and the Seiko's carries a magnifier over the date. This row is a tie, though sapphire is a stronger point at $370 than at $900.

## Accuracy

This is where the Orient's usual advantage disappears. Orient rates the F6722 at +25/−15 seconds a day. Seiko rates the 6R35 at exactly the same +25/−15.

Against Seiko's 4R calibers, rated at +45/−35, Orient usually wins this row. Against the 6R35, there is nothing to choose. A rating is the tolerance a maker will accept, not a promise about any single watch, and our guide to [reading a watch spec sheet](https://wristmetric.com/culture/how-to-read-a-watch-spec-sheet) explains how to weigh it. This row is a tie.

## Water Resistance

Both are rated to 200m. The difference lies in what each maker says that rating means.

Orient lists the AC0Q Diver II as water resistant to 200m. It does not call it a diver's watch or claim ISO 6425, the international standard for divers' watches, despite the word "Diver" in its name.

Seiko lists the SPB177 as a 200m diver's watch. Seiko's instructions for its 6R35 diver's models say the watch "can be used for air diving" within the range shown on the dial. Air diving means recreational scuba on compressed air, as distinct from the saturation diving done by commercial divers. We could not find explicit ISO wording on the SPB177's own page, but Seiko's diver's designation is a claim Orient does not make.

Why does it matter? An ordinary water resistance rating is a test pressure applied to a sample of new watches. The ISO diver's standard calls for each watch to be tested, and adds requirements for a timing bezel, legibility in the dark and resistance to shock and magnetism.

> Both watches are rated to 200m. Only the Seiko is rated for diving.

The people who need that are scuba divers, especially anyone who would time a dive on the bezel or wear the watch as a backup to a dive computer. For swimming, snorkeling and daily wear, the Orient's 200m rating and screw-down crown are more than enough. Within Orient's own range, the ISO 6425 rated option is the Orient Star Sports Diver RE-AU0301B00B, listed at $700 but out of stock at Orient Watch USA when we checked.

The Seiko wins this row.

## On the Wrist

This is the Orient's strongest ground. A 39.9mm case with a 46.5mm lug-to-lug will suit almost any wrist. That lug-to-lug figure is shorter than the 47mm of Orient's own 41.8mm [Kamasu](https://wristmetric.com/reviews/orient-kamasu-review).

The Seiko's 52.6mm lug-to-lug is long. Lug-to-lug length usually decides whether a watch overhangs the wrist, and on a smaller wrist the Seiko's lugs may extend past its edges. Its 45mm diameter adds to the presence. The two are within 0.1mm in height, so neither has an advantage under a cuff, but on paper the Orient will fit many more people.

## Quality

The Orient comes on a 316L steel bracelet with a fold-over clasp and a diver's safety. It has a flat sapphire crystal, a screw-down crown and a solid screw-down caseback, which is a sound specification at $370. Orient lists a stainless steel bezel without naming the insert material.

The Seiko's bracelet closes with a three-fold clasp with a secure lock and an extender, which lets the bracelet open wide enough to go over a wetsuit sleeve. Together with its diver's rating, that makes it the more purpose-built tool, and it takes Best Build.

## Long-Term Ownership

Both carry 3-year US warranties. Seiko's covers purchases from July 1, 2024, through Seiko or an authorized US dealer, and with the SPB177 missing from Seiko's own store, confirming the dealer matters.

The Seiko's 70-hour reserve is an advantage that lasts as long as the watch is worn. Both have sapphire crystals and screw-down casebacks, so neither should age badly through ordinary wear.

## Value

At $370, the AC0Q Diver II brings a sapphire crystal, 200m of water resistance, a screw-down crown, a 120-click bezel and the same accuracy rating as the Seiko, in a 39.9mm case. That is an unusually complete specification at its price.

The SPB177 asks $530 more. In return it adds 30 hours of reserve, a diver's rating for air diving, a clasp extender, a date magnifier and a more distinctive case. Those are real advantages, and for a diver they are the right ones. They also come in a case that many wrists will find too long.

For other Orient and Seiko diver matchups, see [the Kamasu against the Prospex SRPF03](https://wristmetric.com/comparisons/orient-kamasu-vs-seiko-prospex-srpf03) and [the Mako against the King Turtle](https://wristmetric.com/comparisons/orient-mako-vs-seiko-king-turtle).

## Verdict

- Best Value: Orient AC0Q Diver II
- Best Movement: Seiko Prospex SPB177
- Best Build: Seiko Prospex SPB177
- Editor's Pick: Orient AC0Q Diver II

The SPB177 is the better dive watch. It earns Best Movement for a 6R35 that runs for 70 hours at the same accuracy rating as the Orient, and Best Build for a diver's rating for air diving and a clasp made to go over a wetsuit. If you scuba dive, your wrist suits a 52.6mm lug-to-lug and you can find one from an authorized dealer, it is worth the extra money.

For everyone else, the AC0Q Diver II is our pick. It matches the Seiko's accuracy rating, crystal and depth figure, fits a far wider range of wrists and costs $530 less. The Seiko's advantages are real, but its diver's rating and extender pay off only underwater, and its 70-hour reserve comes in a case many wrists will find too long.

Prices are US dollars as charged by the maker at publication. Verify specifications with the manufacturer before buying. Editorial policy: https://wristmetric.com/editorial-policy/