So I've been in and around the kink lifestyles for a long while and only recently have I started learning of the keyhole tattoo. Now that could also be that the freeuse community is pretty fringe so may be older than I realize. There was always talks about recognized symbols or something that would tip others off to your preferences. But as far as freeuse went it seemed hazy at best. A keyhole is such an innocuous tattoo and there's so many styles and reasons to get one. So there's always going to be some trepidation and it honestly feels like something that got started on a whim. But even if there was an unmistakable sign or accessory that conveys someone is freeuse you should always at the least make sure both parties are game with a quick discussion. If anything to decide where to go and fuck lmao.