Speed cameras

Does anyone know what metal static speed cameras are made of?
I’ve ordered some signs and i think i’ve made a ■■■■ up.
The plan is to advertise my business on the back of a speed camera. The thing is i didn’t ask for magnetic signs, I just thought i’d use no nails, But i think they’d arrest me for criminal damage if i do.
If they are made of steel i can re order and get some magnetic ones.

Cracking idea don’t you think?