A couple of weeks ago, the wife and I mailed in our application for renewal passports to Philadelphia.
Yesterday, I received a notice from UPS that a package would be arriving, overnight, by 10:30am today.
A package did arrived and it contained this.
To me it looks like a '+' key for some kind of keyboard or machine.
This picture is 3 on these, showing the back, front and side. The '+' is spring loaded.