I believe SOG stood for Studies and Observations Group back in the Vietnam era but now it stands for Special Operations Group and thats why they make the seal line of knives...at least my take on it
I went to the sog website and found this:
The SOG Story
SOG originally stood for Studies and Observation Group, an elite joint services military group designed for covert operations in the Vietnam War. Sanctioned to develop and purchase their own equipment, SOG created a knife for use in one of the harshest environments in the world. It is in the spirit of this elite group that SOG Specialty Knives was founded.
Totally committed to creating the world's finest specialized knives and tools, SOG became the first knife manufacturer to expand its line to include a broad scope of fixed blades, folding knives and multipurpose tools. Each product is created by Founder and Chief Engineer, Spencer Frazer. His patented inventions and unique, futuristic style have earned SOG many awards and Frazer the recognition as an industry innovator and premier designer.
Today, SOG products are distributed around the world and renowned for their uncompromising style and performance.
MACV/SOG History
SOG Specialty Knives and Tools, Inc. was named in honor of the Vietnam War's only covert special warfare unit-The Studies and Observation Group. Its existence was once denied by the US Government and it wasn't until long after the war that the SOG Story could even be told.
The following is an excerpt from US ELITE FORCES-VIETNAM by Leroy Thompson that further describes the nature of this specialized group and its secret missions.
Separate from "conventional," unconventional operations of the 5th Special Forces Group were the clandestine operations of Military Assistance Command Vietnam/Studies and Observations Group (MACV/SOG). The Studies and Observation Group (SOG) was a cover name to disguise SOG's real function, and the name "Special Operations Group," as it was sometimes called, described its real mission more accurately.
Activated in January of 1964, SOG was a joint services unit composed of members from all four branches of the armed forces, including Navy SEALs, Marine Recons, Air Force Special Operations pilots of the 90th Special Operations Wing, but predominantly Army Special Forces.
MACV/SOG's missions included: cross border operations into Cambodia, Laos and North Vietnam to carry out intelligence gathering or raiding missions on the enemy's 'home ground'; gathering intelligence about POWs and carrying out rescue missions when possible; rescuing downed aircrews in enemy territory ("Bright Light" missions); training, inserting, and controlling agents in North Vietnam to gather intelligence or form resistance groups; carrying out 'black' Psy Ops such as operating fake broadcasting stations inside North Vietnam; kidnapping or assassinating key enemy personnel; retrieving sensitive document so equipment lost in enemy territory or in enemy hands; and inserting rigged mortar rounds or other booby-trapped ordnance in enemy arms caches (OPERATION ELDEST SON).