Up to the dedication of Interstate 49 in December 2012, Missouri always included the state name in standalone shields (i.e., not a part of other signs such as a "big green sign"). But it appears that most Interstate 49 shields don't have the state name, such as these photographed by Matt Roberds in Joplin the day of the I-49 dedication. This assembly is on 32nd Street at Interstate 49 and US 71.
Photo courtesy of Matt Roberds