Puzzler from another site

You guys are pretty clever at figuring stuff out (I think of the time
Wolfgang posted some random picture and we all narrowed down the
location to a few meters).

This picture http://img.photobucket.com/albums/v8...1/pic1940a.jpg
was posted on rec.puzzles on a regularly occurring thread, "What is
it?" It's an unknown, so there is no answer forthcoming. The only clue
is that it was found on a beach in Ireland....it measures about 8
inches on a side. Any ideas?

--riverman