It is the real McCoy! Amazing ain't it :-)

It came from somewhere close to this one

http://www.themodernantiquarian.com/browse.php?site_id=1283

I first heard of it a couple of weeks ago when I picked up a second hand copy of Sean P O'Riordain's "Antiquities of the Irish Countryside", which has a picture of it sub-titled

"Megalithic cist from Chapelizod, co. Cublin (now in Dublin Zoological gardens, Dublin)"

Plate 73, in between pages 136 and 137.

The photo I saw is from when it was in its original position, but I have the 5th Edition of the book (pub 1979). The book was first published in 1942.

There. That gives it some pedigree :-)

What a cracker eh?