This is the most challenging of the 4 caches. Go to Don's Landing, go past the "Warning sand dunes unstable" sign (at your own risk), there is a small peninsula with a rusty metal pole. Stand by the pole with your back to the ocean and look down and to your left. There is a tiny cave the size of a large shoebox, inside is a metal mint box with a combination padlock inside a plastic bag.
The combination is on the logs of the 3 other caches.
There is a metal 50 year calendar hidden inside for the first person to claim.