I have this on my Irish National. PiobBear has a much nicer one as a badge on his caubeen.

Mine came from the Antietam museum store (Sharpsburg to us Yanks of a southern persuasion). It is a tad on the heavy side, but quite affordable; so I got another for my Irish-descended bride.

I've posted a link before, but here is mine, in its native habitat.