As the banner says, if you qualify, you can log it. All OCNA Challenge caches are locationless type, arranged as Geo-Art in The Gulf of Mexico.They are all "unknown" (?) caches, owned by a special Admin account, OCNAChallenges. Do you have an idea for one? Feel free to contact us.
Finder level 3: Very simple. Find any 100 caches listed on the OpenCaching North America website!
Verification: For the "Finder" challenges, you need do nothing really, except qualify, as your find count is displayed in your profile. Keep in mind that for many other of our challenge caches, we do have the equivalent of a Groundspeak "my finds pocket query", and that .gpx file is easily imported into GSAK, or any similar stats program.