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Article: SII and TMI movements: What's the differences?

SII and TMI movements: What's the differences?

SII and TMI movements: What's the differences?

This blog provides a brief explanation of SII and TMI in the watch manufacturing industry. SII refers to Seiko Instruments Inc., which is a member of the Seiko Holdings Group and produces movements labeled with the "SII" logo. TMI stands for Time Module Inc., which previously sold movements manufactured by SII and Epson. However, it has now merged with Seiko Instruments, making a TMI movement similar to an SII movement.

WHAT IS SII, TMI? Which one is better?

Seiko Group Corporation is a conglomerate that controls various subsidiaries, including SII and TMI.


The SII is for Seiko Instruments Inc., based in Chiba, Japan.


The trademark TMI was previously owned by a Hong Kong-based company called Time Module (H.K.) Ltd. However, since 2015, it has been fully acquired by Seiko Group. While Time Module (H.K.) Ltd has been replaced by SEIKO Manufacturing (H.K.), they have decided to keep the TMI brand name.

This is from TMI: “Time Module (H.K.) Ltd. was established in 1987 with original funds from Seiko CorporationSeiko Instruments Inc., and Seiko Epson CorporationEffective from the 1st of December, 2015, Time Module (H.K.) Ltd. is wholly-owned by Seiko Holdings Group and is dedicated to offering high-quality watch movements manufactured by Seiko Instruments Inc.


Seiko has released a statement announcing that Seiko Instruments will be merging with Seiko Watch Corporation on April 2nd, 2020. Both Seiko Watch Corporation and Seiko Instruments, Inc. are owned by Seiko Group Corporation. Seiko Watch Corporation focuses on planning and sales for the Grand Seiko and Seiko brands, while Seiko Instruments, Inc. mainly handles the production of mechanical watches. 


SII and TMI are both trademarks owned by the Seiko Group. This is why you may notice their name being used interchangeably with the Seiko name on various movements. The difference in name only reflects the structure of their business, such as distribution, reselling, and marketing. However, the underlying movement of the product remains the same Seiko movement. Essentially, SII, TMI, and Seiko are all just different names for the same thing.

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