This Seiko World Time 6117-6400 is a distinguished vintage timepiece from the early 1970s, renowned for its dual-time functionality and unique "error bezel" variant. This model is particularly notable for its association with the British Standard Time experiment (1968–1971), during which the UK remained on GMT+1 year-round. Reflecting this period, certain bezels display London and GMT as separate time zones—a rare and collectible feature among enthusiasts.​ 
 
Key Features:
 
Movement - Equipped with Seiko's automatic Caliber 6117B, the watch offers reliable timekeeping with a date complication and a 24-hour GMT hand, allowing tracking of a second time zone.​
 
Case - Crafted from stainless steel, the case measures 41.0 x 45.0 mm, providing a robust yet comfortable presence on the wrist. The watch features a plexiglass crystal and is not water-resistant.​
 
Dial - Available in black, silver, or white, the dial includes a rotating inner bezel marked with 24 global cities, facilitating quick reference of world times.​
 
Bracelet - Originally offered with steel, leather, or rubber straps, the watch accommodates various styles and preferences.​ Functions: Beyond standard timekeeping, the watch provides date and GMT functionalities, enhancing its practicality for travelers and professionals.​
 
Historical Context - Between 27 October 1968 and 31 October 1971, the British government under Prime Minister Harold Wilson implemented the British Standard Time experiment, maintaining the UK on GMT+1 year-round. During this period, Seiko released a version of the World Time 6117-6400 watch featuring an "error bezel," where London and GMT were marked as separate time zones instead of being aligned. This design choice likely reflected the UK's temporary alignment with Central European Time. After the experiment concluded in 1971, Seiko updated subsequent bezels to correctly position London and GMT within the same time zone.