Longines Caliber L888.6 Watch Movement

Brand	Longines
Caliber Number	L888.6
In-House?	No
Base Caliber	ETA A31.L11
Movement Type	Automatic, self-winding mechanical
COSC?	Yes
Lignes	11.5”’
Diameter	25.6mm
Height	3.85mm
Jewels	21
Power Reserve	~72 hours
Lift Angle	51 degrees (unconfirmed!)
Vibrations Per Hour	25,200, 3.5Hz
Shock System	Nivashock
Balance Spring	Silicium (silicon)
Rotor	Ball bearing system
Winding Direction	Bi-directional
Hacking?	Yes
Hand-Windable?	Yes
Hand-Count	3
Features	Central hours; central minutes; central sweeping seconds
Country of Manufacture	Switzerland, Swiss made
Known Models	Longines Legend Diver – Black on bracelet (ref: L3.764.4.50.6), Black on brown leather strap (ref: L3.764.4.50.0), Blue on bracelet (ref: L3.764.4.90.6), Blue on blue strap (ref: L3.764.4.90.2) (Add your watch in the comments below…)

Longines caliber L888.6 is 3-hander, time-only automatic watch movement. It is Swiss made with 21 jewels, produced by ETA (Swatch Group). Although this movement is based on the ETA caliber A31.L11, the L888.6 is exclusive to Longines.

39mm no-date Legend Diver models powered by the cal. L888.6 were introduced in November 2023.

Caliber L888.4 VS L888:

There is a similar caliber L888 (without the .6). Both movements are based on the ETA A31.L11, with the main difference between the two being that the L888.6 is a Certified Chronometer (COSC) with a silicon balance spring.

L888 is also the base caliber number. See more L888 variations here.

Silicon Balance-Spring:

As mentioned above, one of the Longines caliber L888.6’s notable features is its use of a silicon balance-spring (hairspring). With so many magnets being used in modern everyday accessories and appliances, magnetism is one of the most common threats to the accuracy and functionality of a watch. Using silicon for the balance-spring makes it antimagnetic.

As Longines describes it:

“Silicon is lightweight material which is resistant to corrosion and it unaffected by normal temperature variations, magnetic fields, and atmospheric pressure. Its unique properties enhance a watch’s accuracy and longevity.” –Source

To reinforce the importance of magnetic resistance in a watch and its impact on a timepiece’s overall performance, Longines has extended their manufacturer’s warranty to 5 years on all watches with a silicon balance-spring (announced 9/2020 – source).