This Missouri sign assembly, on Missouri 15 and 22 at US 54 in Mexico, is a bit more complex than usual. Up ahead is a junction with supplemental route D, which serves as a frontage road for US 54. Missouri almost never mixes arrow pointers and JCT signs, but it happened here.
At the time this photo was taken, in March 1998, the Missouri 15 and 22 signs were different than usual. The font (FHWA Series B) was narrower and thinner than those usually found on Missouri signs (FHWA Series C). The state outline was a "pointy" marker that doesn't match the state outline quite as closely as the usual state highway marker.
The close-up on the right shows the unusual nature of these markers more clearly. These markers were replaced with standard Missouri markers sometime between January 1999 and July 2002.
A side-by-side comparison of the two types of markers can be made on Missouri 79 at Interstate 70 in O'Fallon. In addition, there was a wide version of a similar marker on Missouri 763 in Columbia, also replaced before July 2002.