The Sea-Gull ST2500 is an automatic calibre produced by Tianjin Sea-Gull, one of China's largest and most established movement manufacturers. Operating at 21,600 bph with 25 jewels and approximately 45 hours power reserve, it features an open-heart architecture — the balance wheel is visible through an aperture in the movement, producing the oscillating mechanical display characteristic of open-heart watch designs. The V2 designation refers to the second-generation modification of this calibre by replica manufacturers for tourbillon-style references: the balance wheel aperture is configured with a tourbillon cage aesthetic, giving the visible rotating mechanism the appearance of a tourbillon complication.
It is important to understand what the ST2500 V2 delivers in a tourbillon-style replica. A genuine tourbillon is a complication that rotates the entire escapement assembly to counteract the effects of gravity on timekeeping accuracy — it is one of the most mechanically complex and expensive complications in watchmaking. The ST2500 V2 is not a tourbillon movement. The rotating element visible through the dial aperture is the balance wheel within a decorative cage — it oscillates and rotates as the movement runs, producing a visually compelling display, but without the gravity-compensation mechanism of a genuine tourbillon. Buyers who specifically require a genuine tourbillon should be aware of this distinction before purchasing.
In Practice
- The ST2500 V2 operates at 21,600 bph with 25 jewels and approximately 45 hours power reserve — the longest power reserve among Sea-Gull calibres used in replica production. The movement is self-winding through wrist motion with bidirectional winding rotor, and includes hacking (stop-seconds) for precise time setting.
- The open-heart architecture is a factory design feature of the ST2500 — the balance wheel is exposed through an aperture in the movement bridges. The V2 modification adds a decorative tourbillon cage around this aperture, framing the visible rotating balance wheel in a tourbillon aesthetic without adding tourbillon mechanics.
- The rotating element visible through the dial is the balance wheel — it oscillates at 21,600 bph and is genuinely visible and in motion during normal watch operation. The visual effect of a rotating mechanical element through the dial aperture is real; the tourbillon gravity-compensation function is not.
- The ST2500 is a Sea-Gull calibre with an established track record in the broader watch market beyond replica production. It is used in Sea-Gull's own branded watches and carries better serviceability characteristics than smaller Chinese clone movements — parts and service knowledge are more accessible than for Mingzhu calibres of comparable complexity.
- The V2 designation reflects replica manufacturer modifications to the base ST2500 for tourbillon-style reference compatibility — cage fitment, dial aperture alignment, and case geometry adjustments specific to the reference. The ST2500 V2 is used in both closed caseback and exhibition caseback configurations depending on the specific reference.
Related Terms
Sea-Gull ST1655 V3 · Miyota Movement · Mingzhu DG2813 V4 · Super Clone · Sapphire Crystal
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For a full overview of movements used in replica watches — including how the Sea-Gull ST2500 compares to other calibres — read: Replica Watch Movements Explained