Stamp (Mario's Time Machine)
From the Super Mario Wiki
The Stamp is an item in the PC release of Mario's Time Machine. It is a postage stamp issued in the United States of America circa 1752 (even though the first postage stamps outright were available in 1840, and the first American postage stamps in 1845). Mario receives it from Deborah Read in Philadelphia after traveling back in time to 1752, who gives it to him for free but trusts that he is going to pay her back with a Penny whenever he can (he later does so). Mario then brings the Stamp to a librarian so that he can be put on the library's mailing list. The librarian assures Mario that a copy of Benjamin Franklin's Almanac is going to be sent to him via the mail in a few days (it should be noted that Mario does not have a house or any address to himself in Philadelphia circa 1752).