It is a lovely piece, probably looks smaller in the photos than it actually is. I've been trying to find out more about it since I saw a pic of it here: http://www.carlowcountymuseum.com/archeology/index.html (scroll down to the annoyingly fast gif animation), looks like it's been moved recently.

I had a hunch it was still there but was still taken aback when I did actually find it. It's on the eastern slope of the hill and would probably be nicely lit early morning around the equinoxes. There is a cairn marked on the map higher up the hill, on the summit. Perhaps it came from around there.