I like wax stamps. They are a bit unpractical, but add a little bit of personality to snailmail. You feel a bit special when you get to crack open that seal. Also the bright colours with the muted brown has held a strong attraction for a while now.
As part of a master's thesis design project at the Basel School of Design in Switzerland, Purrington developed new versions of U.S. currency. He based his designs on his study of other world currencies and America's currency history.