Photos courtesy of David Backlin (taken May 2003)
Missouri 13 was the latecomer, so to speak, when it was rerouted along US 160 between Springfield and Reeds Spring in November 2002. In order to avoid replacing signs along the James River Freeway in Springfield, standard non-freeway markers were appended to the large green freeway-standard signs for exits. They would seem to be easily overlooked because they're so small compared to the standard freeway signs. They're even hard to see in these photographs.
David Backlin revisited the area in November 2005, and found that the sign at the exit had been replaced, giving US 160 and Missouri 13 equal status on the sign.