According to this page on Wikipedia, YEMA was owned by Seiko between 1998 and 2005. During this period, YEMA watches were powered by Seiko movement with the most popular being the automatic YEMA Sea Spider which was powered by the Seiko 4S15 movement.

Below are a few images taken from an old YEMA catalog that featured the Sea Spider. The catalog dates back to year 2000 and contains some marketing literature on the watch.
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