how can you tell (by vin/#) if a taurus was a police car?

[cop-car mechanic]

i know crown vics have a "P71'" vin code...but how do you tell a taurus 'police' from a everyday car? i want to add one to my collection of police cars, but dont know how to 'tell'... little help, plz?? (know any 'sites' or clubs ?) thanks.