One of the major draws of Seiko’s 6619 automatic line - like the 1968 Seiko 6119-8100 MACV-SOG Arabic dial automatic sport diver here, with vintage Waltham military compass, NOS USMIL strap, and MACV-SOG patch - were their amazingly simplistic dials and hands.  These combine to form its single greatest aesthetic quality – symmetry. 
 
But what else is significant about this Seiko 6119-8100...
 
Ah yes – this is one of at least four separate Seiko automatic dive watches utilized by the U.S. Military Assistance Command Viet Nam – Studies and Observations Group (MACV-SOG) used by U.S. Special Forces during the conflict.  During the era these were made, Arabic numeral dial designs were rare and quite the departure from the norm.  It’s a safe assessment the Arabic numerals were one of the aspects MACV-SOG favored, and USMIL forces assigned to the secretive group were either issued these watches or instructed to purchase them at the PX before a covert ops tour.
 
A highly classified multi-service USMIL Special Operations unit, MACV-SOG conducted covert unconventional warfare operations prior to and during the Viet Nam War.  The unit conducted cross-border operations from Viet Nam into neighboring Laos, Cambodia, and North Viet Nam, with the USG infamously denying its existence until declassified in 1997.  SOG operations levied a high toll on North Vietnamese logistic supply lines and bases in Laos and Cambodia following the early 1968 Viet Cong Tet Offensive.  But to operate in a non-attributable manner in these countries – where the USMIL wasn’t supposed to be – required atypical equipment.
 
Established in 1963 and principally run by Conrad “Ben” Baker, the USMIL's Okinawa, Japan-based Counter Insurgency Support Office’s (CISO) main mission was to issue standard and untraceable (read, sterile in appearance to offer a fig leaf of plausible deniability when USMIL forces were operating somewhere they weren’t supposed to be in the countries in and around Viet Nam) gear, clothing, and weapons to Special Forces in Vietnam, to include the USMIL’s MACV-SOG.  It would cease operation in 1973, following the U.S. withdrawal.
 
The story of CISO and Ben Baker, these Seiko watches, and the work of SOG operatives is told by Frank Greco in his book, “Running Recon: A Photo Journey with SOG Special Ops Along the Ho Chi Minh Trail.”  The Seiko 5's ordered by Ben Baker have become much sought after in vintage military and Seiko collecting communities.  Want more on the MACV-SOG use of Seiko?  Read these two Watches of Espionage articles, here and here.
 
Per Greco’s tome and our additional in-depth research, SOG forces used four different Seiko references.  Some were CISO-issued beginning in circa 1968 and some preceded this time (so-called “Pre-CISO” watches) – beginning with the Ref. 6619-8xxx (first the 6619-8280, then the 6619-8060);, followed by the 6119-8100, 7005-8030, and the newly-discovered 6106-8100. 
 
And a late 1960s Seiko 6119-8100 model (not this exact example here) was issued by CISO to SOG legend John Stryker Meyer, aka “Tilt,” per our communication with him during our research into the Watches of Espionage article we researched and wrote on the MACV-SOG Seiko's.  Related, author and Navy SEAL Jack Carr interviewed Tilt - where both extolled the virtues of Seiko watches - on his great podcast, Danger Close, here.
 
Per WoE, "When it came to equipment, SOG recon men were issued the most innovative tools, often custom tailored for clandestine and covert reconnaissance.  Meyer received his watch from S4 unit supply specialists after arriving 'in country' in April 1968.  There was no fanfare, the issue process of the watch was no different from that of a CAR-15 rifle, a tiger stripe camo uniform and a PCR-25 radio: it was part of the standard kit..."
 
"Meyer recalls the Seiko being issued on a black tropic strap and due to the bright glow of the tritium dial, he wore the timepiece on the inside of his right wrist, noting that 'the luminous dial was so bright that SOG recon men had to cover it with gloves or black electric tape at night.'  Meyer preferred the watch over the Rolex Submariners many of his fellow SF soldiers purchased, because of the bright tritium lume and the practical day/date function."
 
"It was a tool, and as he recalled over a half century later, 'even in the pitch black jungle, I knew when to make communication checks with the airborne command aircraft– usually at midnight, or at 2 a.m.'  For MACV-SOG operators like Meyer, timing was everything.  Meyer said that some of his fellow Recon Company soldiers added a Waltham Clock Company compass to the strap, but he preferred the traditional compass around his neck." 

This Seiko 6119-8100 MACV-SOG comes on a NOS USMIL nylon strap, and with nylon strap, springbar tool, SOG patch, vintage Waltham compass, and rugged travel case.