Headquartered at Frankfurt am Main, German brand Sinn was founded in 1961 by Helmut Sinn. From the earliest days the brand has focused on producing quality dive and pilot pieces with a strong emphasis on streamlined legibility. 

The Sinn U1 is a dive watch that is specifically designed to be a dive piece, first and foremost. Safety, dependability, and integrity are the primary features of this expertly crafted and supremely sporty watch.

First, the case is constructed of Submarine Steel. This special grade of steel was initially created for the outer shell of German submarines and is stronger than the stainless steel typically used in timepieces. It offers an elevated saltwater resistance and delivers a high level on non-magnetism. The case measures 44 mm in diameter and 14.7 mm in height.

The rotating bezel with ratcheted minutes and dive scale is attached to the central section of the case as a “captive bezel” to ensure integrity at great depths. Speaking of great depths, the U1 is rated to a magnificent 1000 m / 100 atm water resistance.

Additional features include a scratch-resistant sapphire crystal, solid caseback, stainless steel bracelet with fold-over buckle, and a screwed-down winding crown composed of rugged Submarine Steel and located at 4 for maximum wrist comfort.

Upon the black matte dial, legibility is priority number one. Look for graphic red and white stylings as well as luminous hands and markers that are easy to read in the dark. There is a date window conveniently located at 3. As a self-winding automatic watch, the ETA 2824-2 caliber can be found in the engine room.

With its masterful construction and its bold stylings, the Sinn U1 is a must-have for connoisseurs of the world’s best dive watches.

Standout feature(s): Magnificent 1000 m / 100 atm water resistance; fabulously strong Submarine Steel case and winding crown; bold graphic dial stylings; “captive bezel” construction; winding crown placed at 4 for comfort.

Details at a glance:

• Model Reference: 1010
• Case Material: Submarine Steel
• Case Dimensions: 44 mm
• Case Height: 14.7 mm
• Movement: Self-winding automatic, 28,800 vph, 25 jewels, power reserve 38 hours
• Caliber: ETA 2824-2
• Complication(s) / Feature(s): Standard time, central seconds, date
• Dial: Matte black color
• Crystal: Scratch-resistant sapphire
• Winding Crown: Screwed-down Submarine Steel
• Water-resistance: 1,000 m / 100 atm (manufacturer's spec), tested to 50 m / 5 atm
• Band: Stainless steel bracelet (will fit up to 7.75 inches wrist)
• Clasp: Fold-over clasp
• Country of Origin: Germany
  
• Condition: Pre-owned in overall very good condition; fully serviced in November 2025; A/R coating has come off in some spots on the crystal; there are some scratches on the metal surface.
• Comments: Includes original box, instructions manual, tool, and warranty card dated in 2008.