Cave Coins Max was a hard difficulty stamp in Club Penguin, only available to be obtained by members. To obtain it, you must find the hidden coins in level 7 of the cave levels in Puffle Rescue.
How to Obtain
Right below the starting tile at the beginning of the level, there is a small arrow pointing downwards. While standing on the arrow, you must take ten steps down, four right, three down, five left, two down, three right, and five down. You will then reach a platform with the coin bag, and a teleporter back to start.
This stamp was released on August 30th, 2010, along with the other Puffle Rescue stamps.