A penile tattoo?

“Back in the day I spotted an image of a chap wearing a chastity device with ink on his glans. If memory serves, it was the letter ‘K’. Can anyone confirm what that refers to?”

"That's right. I come across those pics occasionally on my Twitter feed.", "author": "member_4e3795d05d", "datetime": "2013-03-20T12:58:23+00:00"}