I have an Okapi, and its one of the South African ones. As I understand it, they have not been made in Germany for a very long while. Many years.
The one I have is a medium size, with about a 4 inch blade. I got it from Atlanta Cutlery for all of 10 dollars. because I have a weak spot for "weird" knives from other countries. It does indeed have a ratchet and makes an interesting sound when opened quickly. The knife is in accuality a small navaja, both in shape and mechanisim. The blade lock is very secure. One bad thing is that it came with a very blunt edge. I took it up the road to a knifemaking friend in Frederick and had him reprofile the edge on his belt grinder. It would have been a years work by hand on stones, it was that thick and blunt. BUT- now it cuts like an Opinel and really is not a bad knife. I've had much more "well known" brands of knife that did not cut as well or hold an edge as well. It's about on par with Opinel, the German black cat Mercator knife, and other working knives. Thats the good thing about a simple carbon steel, its a very forgiving material and its very easy to make a low cost decent using knife out of it. Low tech doe'nt mean it don't work.
Try one for nothing else than the novelty of using a centurys old knife design for what it is- a simple knife to cut something.