thirteen knuckles
the journal of Michael Werneburg
twenty-eight years and a million words
Toronto, 2013.05.18
So it seems that "13" tattoos are a thing now. I was only ever aware of the concept in the ironic/comedic sense a la the song "Pretty Fly for a White Guy". Now it's something people actually do, with the knuckles seeming to be the place.
Nutty kids these days.