Credor “Pacific” GCBG973Model: Seiko Credor Pacific GCBG973 4S77 00B0 Year: August 2003 Features: The Movement. At the time, the 4S27 was one of the most complicated automatic movements Seiko made. In the early 1990s, the 4S calibre was born from Seikos desire to recapture the high precision and excellence of their 1970s Chronometer Certified 52 calibre. Delighted with the results of the 4S, Seiko committed to producing 200,000 units their largest single calibre production