Nothing too exciting here with COVID Card 71. Just a wee homage to the triangle, the first non-right-angled-quadrilateral (there’s got to be a single, non-hyphenated word for that — right??) US postage-stamp shape. In 1997, the USPS released triangle-shaped commemorative stamps featuring a clipper ship and a stage coach.
Seven years earlier, They Might Be Giants released their song, Particle Man. This has absolutely nothing to do with the post office (as far as I know), but it does contain a little tale about Triangle Man.