This history was written by my friend AndyFromHonolulu
It's British military...
The strap that collectors call "NATO" (not to be confused with the Rhino, Waterborne, or Zulu straps) is based upon the standard watch strap issued by the British Ministry of Defense (MOD). Called the "G10" by members of the British military because of the form used to requisition the strap (and other items) from inventory, the reason it got its "NATO" name is because the strap has a NSN or NATO Stock Number which identifies this type of strap. Incidentally, the actual military spec strap comes in only one color (Admiralty Grey) and one width (20mm). The hardware specs have not changed (chrome plated brass), though at least some of the straps currently issued have stainless steel fittings. And there are actually TWO NATO stock numbers for the straps: Army/Navy (6645-99-124-2986) and RAF (6645-99-527-7059). If you want to read the actual Defence Standards (or Def Stan), here they are:http://www.dstan.mod.uk/data/66/047/00000200.pdf
Hope this helps,
One thing I would change now in that description is that a couple of years back the MOD changed their specs again, and the current official G10 is 18mm. Depending upon when the strap was made, both 18mm and 20mm straps could be official issue.