(September 1999) Missouri interstate signs still use the state name. Also in the photograph is the state supplementary (not county) marker. Sorry for the blurry photo.
Current style Missouri state route marker. (My collection).
This was a short-lived series in the 1960's that was an interim between the current series and the series below. (Photo by Joe Koehler)
(November 1995) Older style sign hanging in Trenton, MO. There was one of these signs on every block! This series was used from the early 1930's into the 1960's. These signs had Scotchlite reflectorization.
(November 2001) Current style state supplementary sign. The letters repeat from county to county. They can be single or double letters (A or AA).
Older style state supplementary route sign. Notice that the sign identifies the road as a state road. (Photo by Jeremy Lance)