Seiko Prospex \'Tuna\' Quartz Black Dial Black Silicone Strap Mens Watch S23631J1 The Case: This Seiko Prospex Tuna S23631J1 is affectionately nicknamed by Seiko fans as a ‘Tuna’ – because of its larger diameter and bold shape like a tuna tin – loved for decades since its release. The case is made from stainless steel that has been treated to a super hard coating, which ensures extended longevity. In terms of measurements, the case has a diameter of 47.7mm and a thickness of 14.1mm. On top of the black case is a black dive timer bezel which has a unidirectional feature to prevent the timer from being knocked out of place. Also, the markers on the bezel have a luminous coating for an easy to read display. As is seen in other Seiko diver’s watches, a silver crown sits at 4 o’clock which further reduces the chance of a knock. Additional protection is offered through the dial which is sapphire crystal glass which is second only to diamond in terms of its hardness. It has been coated in an anti-reflective material which augments optimum legibility.  The Dial: The uncomplicated lay out of the dial allows for easy readability. The bold hands and hour markers are either coated or filled with Seiko\'s LumiBrite material to allow for readability in areas of low light. A day date window replaces the 3 o\'clock marker, whilst the Seiko logo is present beneath the 12 o\'clock marker. A chapter ring runs around the outer edge of the dial, it features a 60-minute track which allows for more accurate reading of the time.  The Strap: The accordion-style silicone strap combines high durability and comfort – a strap design invented by Seiko in 1975 as a practical solution to the expansion and contraction of a diver’s wrist at different depths. A standard buckle can then be easily fastened to sit comfortably around your wrist. The Functions: Power to the watch is provided by an automatic movement. The calibre used in particular is a Seiko exclusive, called the 8L35. An automatic movement is powered by kinetic movement. Moreover, the calibre has a manual wind capacity whereby power can be supplied by spinning the crown. The watch has a power reserve of 50 hours. It consists of 26 jewels all work independently to provide an accuracy of +15 to -10 seconds per day. Yet another feature of the movement is a stop second hand function which stops the second hand once screwed out. This allows for precision timing in crucial moments. Finally, the watch has a water resistance of 1000 metres, suitable for saturation diving. If you have any questions please  click here Click here to join our  facebook  and  Instagram !