1997 32¢ US Department of the Air Force — **U.S. #3167** was issued 20 years ago today. Click the image to learn more about the U.S. Air Force.

On September 18, 1997, the USPS issued the U.S. Air Force stamp, the first U.S. stamp to have a hidden image using Scrambled Indicia.

Over the years, the USPS had always sought ways to combat counterfeiting, with grills being one of the earliest examples. As technologies changed, they found new, more advanced ways to do this, including microprinting and tagging. Then in 1997, they introduced Scrambled Indicia.

3036 - 1998 $1.00 Red Fox — **U.S. #3036** was issued in 1998 and has microprinting and Scrambled Indicia.

Scrambled Indicia is a pre-press process invented by Graphic Security Systems Corporation. According to the company, it “scrambles, distorts, intertwines, overlaps, or otherwise manipulates images making encoded information on them unreadable by the naked eye, and non-copyable by current color copiers and digital scanners.” These images could then be viewed using a special decoder. In addition to thwarting counterfeiting, the USPS also hoped this interesting new technology could help arouse interest among collectors and inspire new ones.