GC2GDF6

Just come across this one and am of two minds about whether this is a challenge cache or a bonus cache
Simply you have to find 4 other caches (which are challenges with criteria) in each of those there are values for 8 letters which in turn give you the co-ords for this cache
Though it states you do have to qualify and find all the other 4 feeder caches - there is no additional criteria.
Now, while it lists what you need to qualify for those other caches - so seemingly giving a qualifying criteria list this cache - it is for those other caches and isnt asking you to do them all over again for this cache.
So in my mind this is simply a bonus cache and not another challenge cache

Thoughts

In my mind, a challenge cache requires a certain number of finds in a specific category, but doesn't require all of a specific list. All of a specific list (especially if it's a list containing some of that CO's other caches) would be a bonus cache.