Seagull Caliber ST2108

Manufacturer	Sea-Gull
Caliber Number	ST2108
Base Caliber	Seagull ST2130
Movement Type	Automatic, self-winding mechanical
Lignes	11.5”’
Diameter	26mm
Jewel Count	21 jewels (see below)
Beat Rate / Frequency	28,800 bph / 4 Hz (see below)
Lift Angle	50 degrees (unconfirmed)
Power Reserve	~41 hours
Rotor Type	Ball-bearing
Rotor Winding Direction	Bi-directional
Hand-Windable?	Yes
Anti-Shock Device	Novodiac style
Hand Count	4
Functions	Central hours; central minutes; central sweeping seconds; central pointer date; moonphase indicator at 6:00
Hacking Seconds?	Yes
Country of Manufacture	Made in China
Known Models	Sugess Automatic Moonphase (Add your watch to the comments below…)

The Seagull caliber ST2108 is an automatic single-date moonphase movement. This calibre is part of the ST21/TY21 family, which is based on the the ETA caliber 2824-2.

Date/Moonphase Indicator:

Unlike many of the movements made in China, the ST2108 is a true moonphase complication and not just a day/night indicator. The moonpase on the ST2108 is a 29.5 day indicator, controlled by a 59 tooth gear.

The date hand is in the center, and points at the date markers on the outer perimeter of the dial.

Date/Moonphase Setting:

There are two inset pushers on the side of the case: located at 4:00 and 8:00.

• The 4:00 pusher adjusts the central pointer date hand.
• The 8:00 pusher adjusts the moonphase indicator.

Inconsistencies:

As with many of the watch movements that are made in China, don’t be surprised as a lack of consistent information.

Caliber Corner has see the ST2108 advertised as being a 21 jewel movement, as well as a 26 jewel movement. It is also advertised as having a beat rate of 28,800 bph (similar to the ETA 2824-2 that the framework is based on), but also 21,600 bph.

For example, the image below is from the official Sea-Gull store, showing a pointer date/moonphase movement, listed as 26 jewels with a beat rate of 21,600 bph (source).

Watches with the ST2108 can also be found without a pointer date (source)…

The Sugess watches listed on this page (see examples below) are described as having 21 jewels with a beat rate of 28,800 bph. The ST21XX is based on the ETA 2824-2 framework, which beats at 28,800 bph.

The problem (and possibly the cause) is that made in China movements are rarely signed with any identifying information such as manufacturer, caliber number, jewel count, etc.

Examples of watches with this movement:

Additional Resources:

• More Seagull mentions