Yep. It's from a cop car and from quite a while ago too. I had a mate in the Highway Patrol (seriously some of them have mates!) back in the early 80's and went out for a blast in the VK he was driving a few times. The keyring then was one of those rectangular plastic things with the window showing the small card beneath with vehicle details.

I wouldn't be surprised if that was from the 50's or 60's.

It's a cool keepsake anyway.