600 mm by 600 mm (24 in by 24 in) Massachusetts Route shield, made to the specifications of the 1996 edition of Construction and Traffic Standard Details (sign M1-5). Uses the Roadgeek 2005 fonts. (United States law does not permit the copyrighting of typeface designs, and the fonts are meant to be copies of a U.S. Government-produced work anyway.) The outside border has a width of 1 (1 mm) and a color of black so it shows up; in reality, signs have no outside border. The specs actually do not show the curve on the outside border, instead making it a perfect square, but all signs I have seen round the corners.
Own work
SPUI