Could this cave have once been used by smugglers on the Brandy Run? They would certainley have good view of the pad, and there's also a nice view of Ben Crom Reservoir. This can be approached from the pad below, or from the stile near Slievenaglogh Summit above. The cave is at the base of Diamond Rocks so there is no need for any precarious scrambling efforts or rock climbing of any sort (assuming you approach from the right direction). The co-ordinates bring you close to the cave entrance, but you will need a torch and some waterproof trousers to be successful. The container is a large cylinder with a scratch card within for the first to find (but no diamonds). Good Luck.
As with all caches placed in the mountains there is a risk of injury. Weather conditions can change rapidly. It is always better to walk in a group than alone and you should ensure you have the necessary skills and are properly equipped for the terrain.