This aluminium emergency whistle conveniently attaches to your keyring. It's great for security in the outdoors, as well as for everyday use.
It unscrews to reveal a couple of rolled paper tags where you can write your details. But if you screw it back together too tight, the soft rubber o ring seal will squish over the sides which is supposed to stop the paper getting wet.
For storage of personal details its a nifty idea but the primary function as a whistle does not live up to expectations. It is not very loud and is easily overblown to lose most of its volume (perhaps dogs can still hear it when over blown).