During World Wars I and II, most men present in the US were required to register for the draft, regardless of whether or not they were citizens. These cards can be useful in obtaining information about your emigrant ancestor or relative. Depending upon when the individual registered, the registration cards contained information, such as: the registrant’s address, name and address of next of kin, occupation, work address, or general physical description. The cards do not mean that a person actually served in the US military – only that he registered for call-up.
For example, the card shown above is for Charles Jobe, born 28 January 1892 in Cunevo, Italy (province of Trentino). His birth name was actually Carlo Job, and place of birth would have been Cunevo, Austria since Trentino did not become part of Italy until post-World War I. The information on the card shows his place of residence and employment, plus contact info (usually next of kin). Page 2 of the card has his personal characteristics (height, weight, eye and hair color. whether or not bald (he was).
The draft cards can generally be found via online databases (Ancestry, Footnote, etc). Although these databases required a paid subscription, you can generally access them free through your local public library. The Jobe surname spelling for the original Job (or Iob) is not common. I would not have found this record by searching for the usual variants. The good part about using computerized database searches is that you can search by keyword (village name, etc). I found this record by searching for “Cunevo”.