SEIKOLUS Open Heart Black

The SEIKOLUS Open Heart black is a watch you admire as much as you read. A window cut into the dial reveals the balance wheel in motion, the mechanical heart that oscillates constantly and brings your watch to life. Mesmerizing, and unique every time you look.

Inspired by the great collectible watches with integrated bracelets, it pairs the elegance of a refined sporty case with the emotion of partially visible mechanics. Hand-assembled in France around a genuine Seiko NH38 automatic movement, with no date to leave the dial design completely uncluttered.

Technical specifications:

• Genuine Seiko NH38 automatic movement 
• 316L stainless steel case, 40mm (excluding crown)
• Bracelet adjustable with the included adjustment kit
• Sapphire crystal, sapphire caseback
  
• Integrated 316L steel bracelet
• Water resistance: splash resistant (everyday use) — reinforced 5 ATM option available

Personalized to your taste — dial and hand colors, logo or engraved image. Create your custom SEIKOLUS with our configurator.

Comes with a storage box and adjustment kit. 2-year warranty against manufacturing defects. Free tracked shipping — delivered in 8–10 business days.

Custom creation by Time2Seiko — not affiliated with the Seiko brand.

All our watches handle splashes, rain and hand washing. That's enough for normal everyday use.

At checkout, you can enhance that water resistance:

• 5 ATM (50 m) — shower, washing up, heavy rain. Not for swimming.

• 10 ATM (100 m) — pool, sea, snorkelling: you can swim. Not for scuba diving. Available on SEIKOJUST, SEIKODATE, SEIKOMARINER and SEIKO GMT.

ATM stands for atmosphere: 1 ATM is the pressure of a 10-metre column of water, measured in laboratory conditions. These figures shouldn't be taken literally, as moving your arm through water generates far higher pressure. Our usage recommendations are therefore deliberately more cautious than the numbers suggest.

Important: the crown must be fully screwed down before any contact with water. It is the only real entry point for water on a watch. For that reason, our 2-year warranty does not cover water resistance: we cannot guarantee a step we don't perform on your behalf. It does, however, cover any manufacturing or assembly defect.

Case diameter is only a choice on certain models: the SEIKOJUST (36, 39 or 41 mm) and the SEIKODATE (39 or 41 mm). Our other families come in a single diameter, listed in the model's specifications — 41 mm for SEIKOAK, 39 mm for SEIKOCUB, and so on. If no size selector appears on this page, the model comes in one size only.

Which diameter should you choose?

• 36 mm: the most discreet, elegant and dressy. Ideal for wrists of 14 to 17.5 cm. A favourite for a feminine or vintage look.

• 39 mm: the reference size, versatile and unisex. Ideal for wrists of 16 to 20 cm. Our recommended size, classic and sporty at once.

• 41 mm: more presence on the wrist. Ideal from 18 cm up, or if you like a watch that gets noticed.

How do you measure your wrist?

Wrap a tape measure (or a piece of string you then hold against a ruler) around your wrist, just above the bone. Note the circumference in centimetres and pick your size accordingly.

Adjustable bracelet included 🔧

No need to worry about length: every watch ships with an adjustment kit to remove links and fit the bracelet precisely to your wrist. Sizing takes a few minutes, no watchmaking knowledge required, using the small tool included in the box.

Any question about choosing your size? Get in touch, we'll gladly guide you.

This model is made to order and can be customized to your taste.

Hand-assembled for you. Free tracked shipping — delivered in 8–10 business days.

Parts preparation → Assembly → Quality & water-resistance check → Shipping

📦 Tracking number sent as soon as your watch ships. Delivered with a storage box and spare links.

🚚 Free shipping worldwide

All our watches are covered by a 2-year warranty against manufacturing defects, starting from the date of purchase. This warranty covers exclusively material and manufacturing defects. It does not apply to damage resulting from misuse, accident, normal wear, or modification carried out by an unauthorized third party.

To make a warranty claim, you must provide proof of purchase and contact our customer service within 14 days of discovering the defect. Shipping costs related to warranty repairs remain the responsibility of the customer.

We give you 30 days from receipt of your order to change your mind. You can return your watch and be fully refunded, provided that:

• The watch is returned in its original, unworn condition
• It is accompanied by its original packaging and accessories
• It shows no damage or signs of wear

To initiate a return, contact us by email with your order number. Return shipping costs are the responsibility of the customer.

1. Are your watches under warranty?

Yes, all our Seiko mod watches are covered by a 2-year warranty against manufacturing and material defects, starting from the date of purchase. If something goes wrong, we are here to fix it.

The warranty covers material and assembly defects. It does not apply to damage caused by misuse, accident, normal wear, or modification carried out by a third party.

To activate the warranty, contact us with your proof of purchase within 14 days of noticing the defect. Return shipping costs are the responsibility of the customer.

2. Are the watches water-resistant?

By default, all our watches resist splashes and hand washing, water resistance sufficient for normal everyday use. We recommend removing the watch before showering or swimming.

If you would like enhanced protection, we offer a 5 ATM water resistance option, available as an option at checkout. It allows you to wear your watch in the shower and during light water activities, provided the crown is properly screwed down into the case.

3. What types of modifications do you offer for Seiko watches?

Our Seiko mods are fully customizable from A to Z: case, dial, hand color, bracelet type (Oyster steel, Jubilee, rubber, or silicone), bezel, and even your logo or an image engraved on the dial, a service very few makers offer.

Everything is created directly on our online configurator, or through discussion with us by email or Instagram for more complex projects.

4. How can I be sure of the quality of your work?

Every Seiko mod watch is hand-assembled in France, with authentic Seiko movements and premium components selected one by one. Each piece is regulated and inspected before shipping.

We also provide responsive customer service: if you have any questions before, during, or after your order, we are reachable by email and on Instagram. 2-year warranty included on all watches.

5. How can I customize my watch?

You have two options to customize your watch:

– Use our online configurator to create your made-to-measure watch from A to Z: case, dial, hands, bracelet, engraving, logo… Let your imagination run free!

– Or, choose a watch already offered on our site, and at checkout, let us know in the payment instructions which modifications you would like.

You can also contact us directly by email or via Instagram: together we will design the ideal watch, to your taste.

👉 Go to the configurator

6. How long does it take to receive my watch?

Every watch is made to order, specifically for you, in France: assembled, regulated and inspected by hand.

Free tracked shipping — delivered in 8–10 business days. Once shipped, you will receive a tracking email with the parcel number. We ship within France and worldwide, free of charge.