It's no wonder why the Citizen Ref. 4-600851 Y Challenge Diver is renowned for its good looks and robust design. Featuring a 40mm stainless steel case and 20mm wide lugs, this diver’s watch strikes a perfect balance between style and durability.
 
While Seiko experimented with a proprietary locking crown system on the 6105-8110, which ultimately proved flawed, Citizen opted for a reliable screw-down system. This method effectively keeps water out, though the crown tubes are integral to the case. A stripped tube can render the watch practically useless or, at the very least, in need of staying dry. This issue is similar to the problem faced by owners of the late '70s Seiko 6309 diver.
 
The Ref. 4-600851 Y is powered by the 21-jewel caliber 6000 automatic movement, which operates at 21,600 vibrations per hour (vph) and allows for hand-winding. Additionally, it features a quick set date complication, a highly appreciated function that pre-dates similar implementations by many Swiss companies.
 
A distinctive feature of this reference is not only its beautiful vivid green lume but also its red date wheel, adding a subtle yet striking detail. However, the deep crystal without magnification can make the date somewhat difficult to read.
 
The example we have for sale is in new old stock condition, complete with its original Tropic straps, a signed Citizen buckle, the original price tag, instruction manual, and protective film still on the case back. It truly doesn’t get any better than this.
 
The watch currently works flawlessly and will be sold as is. Please let us know if you wish to service it.
 
Ships from Tokyo, Japan