This is a Seiko 5 DX 25-jewel wristwatch from the 61 series. It's a valuable vintage piece with its original stainless steel band. It's in working order and suitable for daily use. It runs overnight after being taken off at night, so there's no need to set the time. The day advance function and push-button date change are also perfect. It's in remarkably good condition for a 57-year-old item. ◇ Model: 6106-7040 SEIKO “5″ DX 25 Jewel ◇ Movement: Cal: 6106 Automatic, 11-type movement, 25 jewels ◇ Production Year: August 1968, made by Suwa Seikosha ◇ Serial Number: 881*** ◇ Case: 42mm long / 37mm wide (excluding the crown) / 11mm thick ◇ Fluted Bezel * Serrated shape ◇ Band: Original SS band with original buckle. Fits wrists up to approximately 185mm (easily adjustable from 185mm to 170mm) ◇ Screw-back case back ◇ Hacking function (the second hand stops when the crown is pulled out) ◇ Day-date function, day of the week in English * Red on Sundays ◇ Day advance function: The day changes one day at a time by pulling the crown and moving it back and forth between 10 PM and 1 AM ◇ Push-button date change ◇ Weight: Approximately 75 grams Regarding the convenient quick-set function, it may cause damage if you use it when the watch indicates between '9 PM and 2 AM'. It is recommended to set the time to around 6 o'clock before using the quick-set function. ◇ While suitable for daily use, an overhaul is recommended for those seeking perfection. ◇ Accessories: None ◇ Last overhaul date: Unknown ◇ Retail Price: 13,000 yen (in 1968) Starting salary for a university graduate: 26,200 yen The production year can be determined from the serial number on the back cover, where the first two digits indicate the last digit of the Western calendar year, and the following letter indicates the month, with O, N, and D representing October, November, and December, respectively. This is a high-end "SEIKO 5DX" model from the Five series, equipped with a Cal.6106 25-jewel automatic movement made by Suwa Seikosha. It features five key characteristics: "shock resistance, automatic winding, day, date, and water resistance." This 61-series movement, which also has a hacking (seconds hand regulation) function, was later inherited by the 52-series King Seiko. It also has a practical date quick-set function by pushing the crown. Thank you.