It has nothing to do with the postal system.
I am not a fan of tattoos, it's a taboo for me. I have a low tolerance for pain and every time I see a tattooed body part I feel the pain. If you want to show off your individuality - wear a t-shirt with a stupid saying. Like the one I used to parade around in. "I'm with stupid", and an arrow pointing to my right. If you want to adorn your body with fine art buy some Native American ghost beads. I have mine and wear them all the time.
When one is 20 something the tattoo is most definitely in North America as one ages the tattoo slips down into South America on the body of a sharpei. You may have to lift the wrinkles and folds to even find the tattoo. So buy a t-shirt, they come in all sizes, colors and you can display your heritage, lack of heritage or your look alike cartoon character.
Back to the Tramp Stamp. I have seen young ladies and some that obviously are having young thoughts with their bar code prominently displayed on their back door. They always seem to wear the correct clothes that only cover up a tiny portion and show the stamp to all that pass by. I have seen these bar codes for years and cringe with the pain that travels down my backside. So, yesterday I heard someone refer to them as -Tramp Stamps - and I nearly fell out of my chair - laughing. I should do a body check on my two girls.
As for me and my body I will continue to wear t-shirts and ghost beads and Livestrong bracelets to own my identity.