Seiko 6118A: A Rare and Overlooked GMT Movement

The Seiko 6118A is one of the lesser-known automatic movements from Seiko’s 6100 series, introduced in the late 1960s. While its close sibling—the 6117—has gained fame among collectors for powering the legendary Navigator Timer, the 6118A remains relatively obscure. However, for enthusiasts seeking something unique, this movement offers a compelling piece of Seiko history.

Background and Purpose

Launched around the same time as the 6117A and 6117B, the Seiko 6118A was created to serve a niche: an automatic GMT movement with a world-time function but simplified for more mainstream watches. It kept many of the same features found in the 6117 series but was produced in smaller quantities and featured slight mechanical differences.

The 6118A powers select Seiko World Time watches, particularly reference 6118-7000 and similar models released primarily in the Japanese domestic market. These watches are now quite rare outside Japan, and many collectors may go years before encountering one in good condition.

Technical Specs

The Seiko 6118A is a 17-jewel automatic movement with the following core features:

• Functions: Hour, minute, seconds, quickset date, and 24-hour GMT hand

• Beat Rate: 21,600 vibrations per hour (vph)

• Power Reserve: Around 42 hours

• No hacking seconds

• No manual winding (automatic only)

The GMT hand in the 6118A is geared similarly to that of the 6117A, rotating once every 24 hours. Most 6118-powered watches have an internal rotating bezel with world cities, enabling the wearer to track time across global time zones.

Key Differences

What sets the 6118A apart is mostly cosmetic and application-based. Unlike the 6117 family, which often included external rotating bezels and sportier designs, the 6118A was generally reserved for dressier world-time watches with more subdued aesthetics.

Some internal parts are shared with the 6117A, making repairs and servicing feasible, though parts specific to the 6118A can be difficult to source due to its rarity.

Collectability

Though overshadowed by the 6117 series, the 6118A is a hidden gem for collectors who want a rare world-time Seiko that stands apart. With its clean design, practical functionality, and historical importance, it’s a testament to Seiko’s innovation during the golden age of mechanical watchmaking.