I have a 21" PC Monitor in my cab and took a 17" one apart last week and both had the shield.
However today I bought a 19", got it home and took it apart only to find no metal cage, I then looked at my desktop monitor and again no cage.
I'm glad I found this out otherwise I would have bought blindly thinking they come with cages.
I want to buy a pallet load of these monitors but don't want to get them only to find they have no cage, they are so much easier to work with when everything is neatly tucked away and safe.