1993 SSP Mustang...anyone know what these tags are?

[USPS SSP]

I own VIN #'s 614, 617, and 623 all of which were owned by the USPS and used by Postal Inspectors. This car along with the other one (listed on dealers website) just came out of service within the last two weeks.
Post Office cars were gently used. No high speed chases, no curb jumping, no countless hours just sitting with the engine idleing. Makes them a wise choice when looking for an SSP IMO.

Also, NO rust California cars !