SSP Mustang identification -Help needed
 

Hi, wondering if anyone knows what federal or local agency in the state of Washington would have ordered a blue on blue automatic car? Car may not have always been an auto, but is currently. Car has kinda been hacked up so not alot to go on. Drivers door was replaced so no tag, owner cannot take a pic of buck tag. Car does have 160 Certified speedo (owner provided pic) and does have yellow trunk release button. Owner stated x-California area car, carfax clearly shows all Washington State history. Kinda stumped on this one. I am going to see car first week of March if owner still has it. My hands are tied till I can see car in person and "hopefully" get to see buck tag info. Any ideas/suggestions would be great. Thanks, Brent