Citizen went 50 years without building a fully mechanical movement, then came back with one they designed entirely in-house. The Series 8 870 is the result: a skeletonized 40.8mm dress-sport watch that lets you see the caliber 9051 from both sides of the dial. It competes on movement pedigree, not Swiss heritage, and that is exactly the point.
What it is
Citizen dominated the 20th century with quartz, to the point where mechanical watchmaking essentially stopped at the company. The Series 8 restarted that tradition in 2021, the first fully mechanical Citizen line in over five decades. The caliber 9051 is entirely in-house: no ETA donor, no Miyota base, built from the ground up at Citizen's Tokorozawa facility.
The open-dial architecture is a deliberate statement, showing both the front display and the caseback simultaneously through a double-sided skeleton construction. For a brand whose watchmaking legacy most collectors associate with Eco-Drive, the Series 8 is a genuine reorientation.
Buying notes
The NB6004-83E uses a sapphire display caseback in addition to the open front dial, but the skeleton design means dust ingress is more of a concern than on a closed-dial watch, so condition of the movement matters when buying used. Power reserve is 50 hours, which is adequate but not generous, and the watch will stop after two days off the wrist. The bracelet finishing on the reference is mixed: polished center links show scratches readily, and integrated bracelets can be costly to replace if damaged.
Sizing at 40.8mm is moderate but lug-to-lug reach runs long for smaller wrists, worth measuring before buying. Citizen's brand ceiling with collectors remains lower than Swiss peers at this price point, which keeps resale values suppressed, though for a buyer intending to wear it that is a feature, not a problem.
Market read
New retail runs roughly $700-900 USD depending on region and retailer. Used examples trade at a discount to that, typically $500-700 in excellent condition, because the secondary market for Citizen mechanicals is thin and brand recognition among resellers is low. For the price, no Swiss brand offers an in-house movement with this level of visible architecture, which makes the Series 8 genuinely good value for a buyer who cares about what is inside the case.
Service expectations
The caliber 9051 is Citizen's own design and service must go through Citizen-authorized centers or experienced independents familiar with Japanese in-house movements. Citizen recommends a service interval of approximately 3-5 years for the 9051, which is standard for an automatic with no complications. Parts availability is good through Citizen's service network, though the open-dial construction means a service tech needs to handle the movement carefully to avoid disturbing the skeleton bridges.
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