One of the first sport diving watches, the Seiko 6106-8100 is one of the lesser-known references used by MACV-SOG operators during the Vietnam War.

Unlike the more frequently cited models (6619-8060, 6119-8100, and 7005-8030), its association with the SOG was poorly documented until the confirmation of operator Michael “Magnet” O’Byrne. His photos and accounts serve as direct evidence that the watch was indeed used in clandestine operations in Southeast Asia by U.S. military forces.

The items used, such as the Seiko watches, were acquired or issued by the CISO (Counter Insurgency Support Office), which was responsible for equipping agents with discreet items that were functionally suited to the jungle environment. The 6106-8100, with its low-reflectivity dial, served this purpose well, as it allowed for sufficient readability without reflecting light—a critical feature for operations behind enemy lines.

O’Byrne wore the watch attached to a compass, forming an essential set for nighttime navigation and survival. He reports that the watch-compass combo was used on every border crossing and that, on one occasion, the compass itself deflected part of the shrapnel from a grenade, protecting his wrist. These details reinforce the 6106-8100’s status as a “mission instrument,” not merely an accessory.

The identification of the 6106-8100 as a watch associated with the SOG expands the historical understanding of military Seikos from that era. Being a less documented model with more recent evidence, it is especially interesting to collectors and researchers. Its confirmation as a watch actually used in combat adds historical value and reinforces its importance within the world of Vietnam-era tool watches.