This is the OG of the NATO strap world. The original NATO strap, as specified by the British MOD, was made in “Admiralty Grey”. Decades later the grey NATO is the most popular colour.
The "NATO Strap" was developed by the British Ministry of Defence (MOD) in 1973. The requirement was to create a watch strap that would be resistant to water (the strap at the time was leather) and would work with the current issue chronograph that had fixed strap bars.
The MOD created the nylon strap, 20mm wide and with an extra flap on the underside of the strap to secure the watch in place.
The great thing about NATO straps is they are easy to change and cheap, so you change them as often as your underwear - students, that means daily!