I had one made up about 15 years ago. Have worn it continuously since then except for going thru TSA security.

It contains my full name, SSN, home phone number (so "they" can call my wife) and "No Drg Allergy"

I originally bought it to wear while motorcycling, hiking,and running.When running I add a house or locker key. When hiking I add a whistle. Now I wear it continuously - just because.

Had one earlier but my home phone area code changed so had to get a new one. ( I wouldn't put medical insurance numbers on it - too changeable)

Wife has her own tags.

The agreement between is that if we might be involved in an airliner crash - if the dogtag is found, that's all the other needs to know.

When I was in the military I didn't have a dogtag. Submariners don't really need them. You either find all of us or none of us.