The location of a tramp stamp is fairly specific, as @GeorgeGlass noted. In general, it’s placed so that wearing pants/skirts that fasten around the waist or even a bit lower would hide the tattoo. Wearing very low-rise pants would, however, reveal the tattoo, as would a bikini bathing suit, thong panties, and so on.
I suppose one could use a tramp stamp as a sort of claim tattoo, but it seems odd that a man possessive enough to ink his woman with a claim mark would place it where she’d have to dress provocatively for it to show. It’s counter-intuitive, I’d think. “If you can see the crack of her ass, you can see she’s mine because the tattoo says so.” Unless, of course, his thing is to have her on display, in which case, go for it.