Yes, they're called "targhe ripetitrici" (repeater plates). They have been used until 2013 in truck trailers, when they got changed to X* *** **, but they're still commonly used in car trailers.
Svesor So, Italy has the same system as Great Britain: the trailer has the same registration as the car?
Before 2013, trailers had to bear both the repeater plate of the vehicle that is trailing it and the actual trailer plate (which is the kind of plate that you can find in this section). After 2013, trailers only need one plate, identical to those of normal cars, with letter combinations starting with X.