What kinds of things are/were written on dogtags?

Yes, they're still used, though the U.S. Army calls them ID tags now. When I was in the Navy, ours had name, social security number, blood type, and religious preference (if any) on them. Other service branches and countries put different information on them, but the reason for them is still basically the same. All US service members are issued two tags: one on a ball chain that they wear around their necks and a smaller one attached to it. In the event of death or serious injury, the long chain remains with the owner and the smaller one is taken for notification purposes.

Most countries issue some form of identification tags to their service members and the purpose remains the same: to help identify the dead and to notify their loved ones. There have been attempts at modernization with the use of computer chips and other information, but metal tags are almost indestructible and remain in use.

A lot of veterans use them as keychains after their service because they are made of stainless steel relatively durable, though you can buy them from outside suppliers now.

The so-called "dog tags" go all the way back to the US Civil War, actually.

Their purpose was to identify a person who has either been killed in action, or was so badly injured that speaking wasn't an option. The basic information on these identification tags included the owner's name, blood type, and religious preference, if any.

All branches of the armed forces issue these tags to enlisted and officers alike. My first husband wore his all the time, because he felt that knowing his blood type could be advantageous if he were involved in an accident.

I believe these thes little metal tags are no longer issue, having been superseded by a computer chip embedded in military identification cards, which can be scammed by a hand held device.

I retired a couple of years ago from the military. At the time I still had dog tags. Dog tags have the persons name, blood type, religious preference (catholic), and ssn. The main purpose of these were to identify a person who has died or been injured.

I once sent a text to a friend under the impression I had wrote "fancy a few quiet pints?" Well predictive text sent "fancy a few quiet shots" I was very surprised when I got to the pub and found my friend at the table with 6 shots of tequila in front of him.

Name, rank, number, blood type, religious affiliation, history of innoculations and whether the bearer is allergic to certain medicines.