Seagull Caliber ST18

Manufacturer	Tianjin Sea-Gull
Caliber Number	ST18, ST18XX, TY26, TY26XX
Movement Type	Automatic, self-winding mechanical
Based On	ETA 2892A2
Diameter	25.6mm
Height	3.91mm
Jewel Count	21/24 jewels
Total Parts	172 components
Beat Rate / Frequency	28,800 bph / 4 Hz
Lift Angle	Unconfirmed
Power Reserve	~42 hours
Rotor Winding Direction	Bi-directional
Hand-Windable?	Yes
Anti-Shock Device	Incabloc style
Regulator	Depends (Etachron style on some)
Hand Count	3
Functions	Central hours; central minutes; central seconds
Hacking Seconds?	Yes
Quickset Date?	Yes
Country of Manufacture	Made in China
Known Models	Sea-Gull 201S, 1076, 1140A  (Add your watch to the comments below…)

The Seagull caliber ST18 is a line of slim automatic movements made in China. It is an ETA caliber 2892A2 clone.

On raw ST18 movements, you likely won’t find any caliber number engravings or inscriptions on the movement or rotor. There is often no branding, not even a jewel count. On some Sea-Gull branded watches, they actually bothered to put the Sea-Gull logo on the rotor.

Tianjin and Seagull are the same company (Tianjin Seagull Watch Group). They have offices in Tianjin, China as well as Hong Kong. The different caliber numbers (ST vs TY) correspond with where the movements ship out of.

Inconsistent/Minimal Information:

As you will find with most Seagull movements (most movements made in China for that matter), there is a lack of official information, technical documentation, and even consistency with the little information that is available.

For example, on Seagull Watch Official’s site, they state the ST18 has a beat rate of 21,600 “times per hour”. Then on Seagull Watch’s site, they state the beat rate is 28,800.

The correct answer should be 28,800 bph, but you will want to put the movement on your watch timing machine to be sure!

You may also see inconsistencies with the jewel counts: some say 21 jewels and others say 24. This is because there are different versions of the ST18, such as the ST1812 – and, again, it doesn’t help that they don’t mark their movements with a calibre number or jewel count, ultimately leading to caliber confusion.

Base Caliber:

The ST18 is based on the ETA 2892A2 framework. It is not an in-house movement.

Yet, you’re bound to come across claims of the ST18 being a “Self Developed Movement”. For example, in this Amazon listing from the official Sea-Gull store.

And here’s one where they call it an “in-house” movement lol.

Note that while there may be breakdowns and ST18 VS 2892 comparisons posted to other sites, there is not enough consistency in these movements to use one comparison as a guaranteed confirmation as to the true differences between the two movements. This is a good one – but it’s also a good example of inconsistency in these movements. The post shows a fixed pin regulator system VS  the ETA using ETACHRON – but looking at the stock image from Sea-Gull above, it appears to use ETACHRON. The point is, take everything with a grain of salt when it comes to these and other made in China movements – especially if you are a new brand and trying to put an accurate product description together – be careful not to inadvertently provide incorrect specs.

Video – ST18 Service Walkthrough:

Examples of watches with this movement:

The ST18 series is available as an off-the-shelf movement, it can be found in various microbrands and mods. The Sea-Gull brand also produces their own watches with the movement.

Additional Resources:

• Learn more about clone movements

Comment Prompts:

Have a watch with the ST18 and don’t know what to say about it? Here are some places to start:

• Does your watch have rotor noise?
• What power reserve are you getting from a full wind?
• Is there any branding?
• What is the regulator like? Is it ETACHRON? Does the micro-adjustment screw actually work?