I already own a KS5626 with the broad 7000 case I love but I really wanted one with the chronometer grade movement.
During the 60s there were accuracy competitions in Switzerland, mainly for Swiss made watch brands but SEIKO started participating since the competitions were open to all brands. Late 60s SEIKO started winning the competition which ultimately led to the death of the competitions and the start of COSC which is Swiss made exclusive. What makes it even more impressive is that SEIKO used their general production watches while many brands only entered with special watch movements made for the competitions.
The 5626 chronometer grade movement is a 28800bph, hack, manual/auto wind, double quickset movement which is said to have had +5/-3 s/d as timekeeping standard which is very good even by today’s measure but especially when you take into account that the COSC 1973 standard was +10/-1. The case has a screw for regulation between the lugs since the case is made in one piece. My other KS5626 keeps +2/-2 on the wrist which is very very good.
The case features “grammar of design” which basically is a design language which states that some angles should be recurring throughout the case in combination with polished and brushed finishes interlaced. If you study the angles you can see that the lines of the bezel and case have parallel lines. Beautiful to study when you know what you’re looking for and of course if the watch is in great condition since it makes for great light play on the case.
I received this watch today and was worried that the crystal wasn’t original since its domed and not flat like on my other KS. Well guess what, my son smashed it and it turns out it’s plexi. SEIKO crystals are hardened and don’t shatter like this. Bad timing but forced me to buy an original crystal for it.