I've never seen that particular model, but I've been using the Schick Extreme 3 for years.

Here is the link to it from the archived version of Schick's website from the late '90's and the early 2000's:
https://web.archive.org/web/19991115202034/http://schick.com/razors_protector_frame.html

Has anyone on this Forum ever used the Schick Protector Razor to shave their head?

Why was my response deleted? 

And type of trimmer will be limited by how close it will get.  But technically, by definition, a trimmer is not a shaver.  It will result in a tight buzz cut.  Some trimmers do cut so close that it may appear to be a head shave, unless looking closely. So most people will still think of it as a head shave.

Another consideration, if you hair is dark, and you have pale skin, the "shadow" left by a trimmer will be very pronounced.  A true razor blade head shave will result in less of a shadow.  Some electric shavers come close to a razor blade.

I've read a few glowing reviews of some devices, not the Vacutrim itself but other brands.  But few claim it would work for head shaves.  Has anyone tried this?