The night-time luminosity is excellent, the watch uses Seiko’s Lumibrite technology, which is an organic luminous material. It is not radioactive and works very well. In any ambient light, the matte black dial with clear, tasteful luminous markers and dissimilar hands ensure that you always have the time at a glance. The absence of shiny metal surrounds for the hour markers keeps the dial look clean. The large arrow shaped minute hand on this Seiko diving watch is effectively differentiated from the hour hand so that I never confuse the two. Luminosity of dial and hands are roughly equal. If anything, the hands appear brighter. The luminous dot and bold triangle on the bezel also assures that you are able to track elapsed time in any lighting condition. The 120 click unidirectional bezel moves smoothly and with just the right tension to assure that accidental turns are minimised. I use that feature every day. I find a watch without a rotating bezel to be less useful unless it is a chronograph. Exposure to sunlight or light high in UV (fluorescent, for example) charges the luminous material, making it environmentally friendly. I have no trouble seeing the time at night. The flat crystal sits slightly below the bezel, which should help prevent scratches. I like a day and date function on a watch. Most diver’s watches don’t display the day and that makes this Seiko diving watch seems an even better choice. I love the blue Saturday and red Sunday.
I swapped out the as delivered rubber strap with a Seiko jubilee style bracelet with flip lock clasp. I found that dresses the watch up nicely and is very comfortable. The strap is great, and conforms to the shape of your wrist after a while, I just prefer a metal bracelet. The crown at 4:00 is large, with fine grooving affording a good grip and is not irritating at all. Thanks to the domed back of the watch, it sits high enough on the wrist so that the crown of this Seiko Diving watch doesn’t form that annoying little callous on the back of one’s hand. For a watch this large, it is surprisingly comfortable. My wrist measures 6 1/2″ around, so I have relatively small wrists. The SKX173 Seiko diving watch crown guard is a visually delightful and wonderfully functional design that I have not seen work as well in any other watch,a terrific feature that is under-reported, IMHO. I remember thinking, on taking the watch out of the box, “Now this is a crown guard… ” It has never snagged on anything. Even if you don’t scuba dive, a Seiko diving watch has a tougher, thicker case /crystal and excellent sealing system, affording maximum protection for the movement within. It just makes sense if you want trouble free operation.
A lot of concern has been expressed about timekeeping, so I should address that. Due to the Seiko Magic Lever winding system and despite the low mass rotor of the 7S26 movement, winding for me is efficient. I have not set the Seiko diving watch in two weeks, and it is currently indicating within a few seconds of the correct time as checked against an atomic clock using just these two simple tricks. In essence, fully wound, a little slow; not fully wound, a little fast. Your mileage may vary. Some combination of rest position and activity level will dictate your actions if you want the watch to be spot on. This is excellent performance for an unadjusted mass produced watch and says a lot about Seiko’s design talents and quality control. The 21,600 BPH (6 ticks per second) movement ensures lower stress than a high beat movement, increasing longevity. The lack of a hack feature can be overcome by applying slight backward pressure on the crown during setting. Care should be used to not have the watch run backward at this point, because that is bad for the escapement. This works best if the watch is not fully wound. I do not often use this approach, since I can speed the watch up or slow it down in use to achieve a good synchronization within a few days.