The MG and MGX prefixes were first used in 1926.
At this time, municipal, county, and state government became unique types.
Until 1958, municipal commercial plates used a different series than municipal passenger car plates, incorporating the X code for commercial.
This practice was discontinued with the tan base in 1959.
1959-1979MG-100A - MG-999Z
MG-A100 - MG-Z999
MG-1000 - MG-9999
100MG-A - 999MG-Z
The 1959/1977 Municipal plates have several different patterns, starting with MG-100A, then MG-A100, MG-1000, and 100MG-A.
Thanks to John Walters for the information on the proper sequence of these.
STICKERED 1973Lee Madigan
These are remakes - made in the mid 70s - of the early 60's issues.
The only known pattern on the 1977 base is MG-000A. These would be remakes (or re-plates ?) of the early 60's issue.