Dogtag around my neck with full name and SSN. Didn't have one in the military but can buy them made as you desire from a few outdoor stores.

Stainless steel so it will survive an airplane crash.

They also make red aluminum ones for if you have a medical issue that should be worn around your neck. (not plane crash worthy though)

Neck chain makes a good place to carry house key and emergency whistle for other occasions.