Cache is not located at Sueno's Stone, but a short distance away within view along with good parking.
Sueno's Stone is a Picto-Scottish standing stone. It measures over twenty feet in height and is comprised of Old Red Sandstone. The name is derived from Sweyn Forkbeard, a 10th century King of Denmark and Norway, with an 11th century reign as King of England to boot. It really has nothing to do with him but carbon dating and accepted opinion dates it to a similar timeframe.
There is a carved Celtic cross and a figure scene on the western side. On the east, four panels which show rows of horsemen, foot soldiers, headless enemies (they'll be the ones what lost then), complete with head pile, and finally the victorious soldiers leaving the battlefield. Each side of the stone has a vine-like design.
Various interpretations of the scene the stone commemorates have been put forward. Some involve various Scottish kings showing dominance. A local tale has the stone as the crossroads where Macbeth first met the three witches.
The stone was encased in the glass display case in the 90s for its protection. Curiously, there are mysterious hints online of an as yet unfound second stone, lost to time.