41 CFR 102-34.145 - How are U.S. Government license plates coded?
U.S. Government license plate numbers will be preceded by a letter code that designates the owning agency for the motor vehicle. The agency letter codes are listed in GSA Bulletin FMR Bulletin B-11. (FMR bulletins are located at http://www.gsa.gov/bulletin. )
Title 41 published on 2013-07-01
no entries appear in the Federal Register after this date.