I must confess, I have never actually seen the 18 round boxes depicted in the photos.
What I can say is.... This packaging is almost certainly Government or agency packaging.
At least as far back as WWII, German and Russian ammunition was issued (in their calibers) in 16 round boxes.
Consider, each pistol was issued as a Pistol, spare magazine, and holster.
So, two 8 round magazines, one box of 16 cartridges equaled a neat issue and no pesky loose rounds.
Personally, I still have oodles of 16 round boxes of Soviet Makarov ammo.