The Tutima M2 Seven Seas S is a compact, 50-bar-rated dive watch, but “40 mm” does not describe every version currently listed. Earlier 6156 models are specified at 40 mm by 12.5 mm, while Tutima Japan’s current collection lists four newer references at 40.2 mm. The bracelet, strap, date display, power reserve and Japanese list price also vary by reference.
Which M2 Seven Seas S does “40 mm” refer to?
The reference matters. Tutima’s model overview documents the earlier 6156-01, 6156-02, 6156-04, 6156-08 and 6156-11 at 40 mm in diameter and 12.5 mm thick. These models include stainless-steel or black PVD case configurations. The same overview identifies an automatic Cal. 330 movement and 50-bar water resistance, with other details varying by configuration. Tutima’s M2 model overview.
Tutima Japan’s collection page lists the newer 6156-10, 6156-30, 6156-21 and 6156-23 at 40.2 mm. Those are close in diameter to the earlier 40 mm models, but the available source does not establish that their thickness is also 12.5 mm. Tutima Japan’s M2 collection.
Current listed 6156 references compared
The following figures are the specifications and Japanese yen list prices shown on Tutima Japan’s collection page. Prices are regional list prices, not a street-price estimate, and listings do not establish global availability.
#1 Best Overall
- Stainless steel case 40mm diameter x 14mm thick; Exhibition case back; Black dial; Luminous hands and hour markers
- NH35A Japanese Automatic movement, 24 jewel; Assembled in Malaysia; Watch weight: 155 grams
- Stainless steel band, 210mm L x 20mm W; Band is adjustable by adding/removing links; Fold over safety clasp
- Mineral crystal; Screw-down crown; Diver stainless steel bezel with black top bezel ring; 200 meter water resistant: Suitable for professional marine activity and surface water sports. Suitable for diving.
| Reference | Diameter | Thickness | Bracelet or strap | Movement and stated power reserve | Date | Water resistance | Japan list price |
|---|---|---|---|---|---|---|---|
| 6156-10 | 40.2 mm | Not stated by Tutima Japan | Steel bracelet | Automatic Cal. 330; 41 hours | Not stated by Tutima Japan | 50 bar | ¥379,500 |
| 6156-30 | 40.2 mm | Not stated by Tutima Japan | Steel bracelet | Automatic Cal. 330; 41 hours | Not stated by Tutima Japan | 50 bar | ¥379,500 |
| 6156-21 | 40.2 mm | Not stated by Tutima Japan | FKM rubber strap | Automatic Cal. 330; 38 hours | Yes | 50 bar | ¥302,500 |
| 6156-23 | 40.2 mm | Not stated by Tutima Japan | FKM rubber strap | Automatic Cal. 330; 38 hours | Yes | 50 bar | ¥302,500 |
The movement, diameter, reserve, date, water resistance, strap and prices in the table reflect Tutima Japan’s listings; thickness is not stated there. Check the current Japan collection page for any changes before comparing prices or availability.
What the hands-on evidence says about wear
In a video review published on December 16, 2022, Peter Kotsa Photographer described being keen to feature the watch “being a 40mm and built to excellent standards.” That is the reviewer’s assessment, not a manufacturer claim. The video description says the review covers build, wearability, bracelet, bezel, movement, lume and functionality, and identifies lume as a shortcoming. That criticism is one reviewer’s opinion, not a verified general performance finding. Peter Kotsa Photographer’s 2022 review.
Rank #2
- ST2130 Automatic Movement: This men's dive watch is equipped with the ST2130 self-winding mechanical movement—a premium 28,800 vph (4Hz) caliber built on the classic ETA 2824-2 design. Engineered for everyday durability, it features shock resistance and a hacking function for precise second-by-second time setting. The movement also supports bidirectional automatic winding, is constructed with 26 jewels, and delivers a power reserve of up to 42 hours
- Fine Workmanship: Our automatic watch case combines marine-grade 316L stainless steel (superior to standard 304 steel) with a domed sapphire crystal bubble glass and cyclops date window (2.5 times amplification effect), featuring inner AR blue coating – creating an indestructible timepiece that maintains crystal clarity in any environment. Designed for professional divers and watch enthusiasts who refuse to compromise
- 20Bar Water Resistant: Our SN0017G-F professional mechanical dive watch delivers true 20Bar/200-meter water resistance, built to meet ISO 6425 dive watch standards. The screw-down crown is a riple-sealed system that prevents water intrusion. And with the double gasket system - Reinforced at crown, case back, and crystal. Suitable for professional marine activities, swimming, water sports, and daily wearing
- BGW9 Blue Light: Its hands and hour markers feature Super Luminous BGW9 blue light, which can last for at least 5 hours in the dark and can absorb and store light energy in a bright environment quickly. Luminous wristwatches allow you to grasp the time without fear of the dark
- Ideal Present for Men: Its precise timekeeping and impressive features, make it a popular choice among professional divers and outdoor enthusiasts. Whether you're exploring the depths of the ocean or simply going about your day-to-day activities, this watch will never let you down, It is a perfect present for your father, husband, or boyfriend
The available information does not provide a measured wrist size, dimensions for the bracelet or strap, or a documented wrist-fit test. A 40 or 40.2 mm diameter alone cannot establish how the watch will sit on a particular wrist. The 2024 article from Dive Into Watches is specifically about the 40 mm model, but its available description does not substantiate additional fit or performance conclusions. Dive Into Watches’ article, published February 22, 2024.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How to choose among the listed variants
- Choose by fit with care: the earlier references are documented at 40 mm by 12.5 mm; the newer Japanese listings give 40.2 mm diameter but no thickness. Try the specific reference and strap or bracelet if fit is decisive.
- Choose the attachment you prefer: the current 6156-10 and -30 listings pair with steel bracelets; -21 and -23 pair with FKM rubber straps.
- Consider the listed reserve and date: Tutima Japan states 41 hours for the bracelet references and 38 hours for the FKM references, and lists a date for -21 and -23.
- Compare price in the right market: the cited ¥379,500 and ¥302,500 figures are Japanese list prices, not a promise of the price or availability in another country.
These are selection differences, not evidence that one reference is universally better. Tutima’s specifications establish a 50-bar rating; the sources cited here do not provide independent dive testing.
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Quick Recap
Best Value
- Stainless Steel case with Black Resin Band
- Black Dial with date window at 3 O'clock
- Luminous markers and hour hands; sweep second hand
- Anti-reverse bezel
- Water-resistant to 200 M (660 feet)
Rank #4
- Round watch featuring corrugated unidirectional bezel, luminous hands/markers, and magnified date window at 3 o'clock
- 40 mm, Length: 210mm, 23k gold-plated stainless steel case with mineral dial window. Movement Caliber: NH35A
- Japanese automatic movement with analog display
- Gold & Stainless steel tone bracelet with foldover clasp with safety closure
- Water resistant to 200 m (660 ft): In general, suitable for professional marine activity and serious surface water sports, but not scuba diving.
Rank #3
- Stainless steel case 40mm diameter x 14mm thick; Exhibition case back; Black dial; Luminous hands and hour markers
- NH35A Japanese Automatic movement, 24 jewel; Assembled in Malaysia; Watch weight: 152 grams
- Stainless steel band, 205mm L x 20mm W; Band is adjustable by adding/removing links; Fold over safety clasp
- Mineral crystal; Screw-down crown; Unidirectional stainless steel bezel with black top bezel ring; 200 meter water resistant: Suitable for professional marine activity and surface water sports. Suitable for diving.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
