To meet the strict engineering criteria of the automatic teller machines (ATMs), the first ATM stamps were made of polyester, a material which is not easily recycled. After successfully test-marketing the stamps in the Seattle and Pittsburgh area for a year, the Postal Service proceeded with research to develop an environmentally sound paper that would meet the same engineering criteria. The result was the EXTRAordinary Liberty Torch stamp, which used 50% recycled paper.