If you go by a traffic cop on a bike, he may do you the favour of using the gun to check your speed. I did. Also the patrol cars have calculated speedos.
A mate went to a station that had highway patrol cars and they checked him out.
They'll never certify any of it, of course, but hey, you're looking to just know how the speeding is reading, right?
How about Grey Ghost for a tag? Or if you remember him, how about Moseby. (Mosebey's Raiders.) Only genuine baby boomers will pick on that one.