This belongs to the final year of the Seiko King Quartz lineup equipped with a single quartz, the catalog year is believed to be 1979.
This 5856-8010 is listed in the Seiko Catalog in Japan, as top of the line in the King Quartz series. A cream-colored dial in a not-so-common 8000 case. Production year is 1978, made for distribution in 1979.
After that year, Seiko had came out with a full lineup with a series of new movement. Highlighting their new technology breakthrough, the Twin Quartz, which brought accuracy to a whole new level. We'll talk about that later.
Eric has been a gadget lover for decades and had been collecting affordable vintage since the nineties. With his passion for vintage watches, he had been sharing thoughts and photos in interest groups, with his intention of raising public interests on forgotten classics.