I noticed the 68k mileage amount. Do you know at what miles they ended the in-service life of this Mustang? Can you tell whether that document was from when the State Police still owned it or after it went to a civilian owner?
The link below will allow you to look up varoius State Trooper license plates.
http://www.statetrooperplates.com/sp-hp.htm
Is the in-service picture you had on Photobucket that actual car or just an example of a CO one in-service? I don't know much about the Colorado cars but didn't notice a plate number like your document on the link above. Not sure if they had unmarked cars or not and whether would have had diff't license plate configuration.
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Mike
1992 Michigan State Police SSP Mustang #5114
1993 Wisconsin State Patrol SSP Mustang
1993 Missouri State Highway Patrol SSP Mustang P641
http://members.fotki.com/MOstang/