To log a "Found It" for this cache (in addition to finding the cache and signing the log) you must have found and logged 100 Puzzle Caches. Demonstrate this logging requirement any way you see fit: reference your profile, lext in the log, attach an image, create a Bookmark list, Challenge Checker, etc.
You are welcome to sign the log and make comments, but do not log this cache as found unless you meet the requirements of having found 100 Puzzle caches and furnished proof as specified above.