Grandfathered challenge -
1 - A minimum of 300 caches is needed to claim the find.
2 - Traditional caches can't be counted.
3 - A maximum of 100 for any cache type is allowed to count towards the final tally. You may have 179 puzzle caches, but you can only count 100 of those towards your 300.
4 - For a cache type to count towards the 300 total, you must have found at minimum 25 caches of that type. So if you have 24 Earthcaches, you can't count any of them towards the total. If you have 26 Earthcaches, they all count towards the total (but remember Rule 3, if you have 101 Earthcaches only 100 count towards the total).
5 - Previous finds count.