Seagull Caliber St3621

Seagull Caliber ST3621

Seagull Caliber St3621

ManufacturerSea-Gull (Seagull)
Caliber NumberST3621
TY3621, TY-3621
Movement TypeMechanical, manual-wind
Beat Rate
21,600 vph
Lift Angle
Power Reserve
Unconfirmed (~45 hours)
Anti-Shock Device
Incabloc clone
Long style regulator
Balance Wheel
Screw style (11mm)
Hand Count3
FunctionsCentral hours; central minutes; small seconds subdial at 6:00
Hacking Seconds?
Country of ManufactureChina
Known Models
(Add your watch to the comments below…)

The Seagull caliber ST3621 is a handwound mechanical movement from the ST36 family of Seagull calibers.

This movement is often referred to as a “Chinese 6498” since it is based on the ETA 6498 framework and made in China.

You may also see this movement referred to as a pocket watch movement.

Some of the topics covered in this caliber listing:

ST3621 VS ST3600:

There is a similar caliber ST3600 with the main difference being that the ST3621 has a small seconds subdial at 6:00 (like the ETA 6498), and the ST3600 has a small seconds subdial at 9:00 (like the ETA 6497).

ST3621 VS TY3621:

Both of the caliber numbers above reference this particular Seagull configuration. It is said that ST movements are from the Tianjin Seagull factory, and TY movements are from the Seagull Hong Kong (HK) factory. With Sea-Gull information it’s usually a crowd-sourced guessing game since not much information is provided officially.

Replacement Prices:

At the time of this post, replacement prices were found in the range of $35.04 to $76.44 USD.

Buy a raw Seagull ST3621 movement here.

Dial Side:

Seagull Caliber St3621 Chinese 6498


The video below shows a Seagull ST3621 being dissembled, cleaned, lubed and assembled again.

Pros and Cons:


Based on a solid infrastructure that has been used for decades; Affordable compared to similar Swiss movements; Easy to work on.


Said to ship from the factory without oil or regulating, therefore if the watch brand doesn’t service the movement during assembly then the watch may have trouble in the future.

Parts for Chinese watch movements are not well-organized and not easy to find, so you may need to get parts from another watch, or swap the movement entirely.

While the China based factories are quick to take designs and produce their own goods from the work of others, they are typically unwilling to share any technical information that can be useful to those seeking to use the movements in a  new watch brand. Therefore, good luck finding any verified spec sheets or tech drawings with factory confirmed list angle, measurements, parts list, etc.

Since the Chinese factories tend to use the same caliber numbers, without marking their movements, it’s hard to tell if your ST3621 was actually made by Seagull.

Additional Resources:

Seagull Caliber St19

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