Seiko's New Limited-Edition Open-Heart Watches Feature 4R38 Caliber and Unique Design

Seiko Japan has unveiled two new limited-edition mechanical watches set to launch in the domestic market for Spring 2026, featuring distinctive open-heart dial designs that showcase the intricate balance wheel movement. According to Instagram user @plus9time, the watches carry references SCVE065 and SSDE025, both sporting elegant light blue dials that immediately catch the eye.

The standout feature of these timepieces is their "open heart" design, which incorporates an aperture at the 9 o'clock position that exposes the balance wheel of the internal movement. This design element offers watch enthusiasts a glimpse into the mechanical artistry that powers these timepieces, creating a dynamic visual element that changes with every tick.

Both models share several key specifications that demonstrate Seiko's commitment to quality and reliability. The watches are constructed with stainless steel cases and come paired with stainless steel bracelets, ensuring durability and a premium feel. The internal mechanism for both references is the Seiko Caliber 4R38, an automatic movement that includes both manual winding and hacking capabilities.

The 4R38 movement operates at a frequency of 21,600 vibrations per hour, contains 24 jewels, and provides a power reserve of approximately 41 hours. This movement has proven itself reliable across various Seiko models and offers a good balance between accuracy and longevity. Additionally, the movement is visible through a transparent case back, which features "Limited Edition" text along with a unique serial number for each piece.

While the watches share many similarities, they differ significantly in their physical dimensions and production numbers. The SCVE065 represents the larger variant, with a case diameter of 42 mm, thickness of 11.6 mm, and a lug-to-lug distance of 51.5 mm. This model has a production run limited to 1,000 units, making it relatively more accessible to collectors.

The SSDE025 offers a more compact option, featuring a case diameter of 34.2 mm, thickness of 10.8 mm, and a lug-to-lug length of 41.4 mm. This smaller iteration has a more restricted production run of just 400 units, potentially making it more desirable for collectors seeking exclusivity.

Both models are rated for water resistance up to 10 bar (100 meters), providing adequate protection for everyday wear and light water activities. The light blue dial colorway adds a contemporary touch to these classically styled mechanical watches, appealing to both traditional watch enthusiasts and those seeking something with a modern aesthetic.

These limited-edition releases continue Seiko's tradition of offering accessible mechanical watches with thoughtful design elements. The combination of the open-heart dial, reliable 4R38 movement, and limited production numbers positions these watches as attractive options for collectors and enthusiasts in the Japanese market, though international availability remains to be confirmed.