Sounds like an old unit especially with a metal knob.

I don't know of anyone having anything now other than plastic knobs.

K-40 units have a metal stem covered with a rotating on/off knob and an outter plastic knob for city/highway settings.

I would upgrade to some nice passport laser diffuser protection now days as alot of departments are using laser instead of radar.

Don't get a laser detector though as all they do is tell you you're getting a ticket without actually diffusing the laser.

The windshield mounted radar units are okay, but those windshield mounted laser units are detectors only.

You need to get the kit that has the two separate laser units which mount on the outside of the vehicle.

I have a k-40 laser diffuser on my truck that works very well, but the passport units are the cats meow.