ACCO parece ser la marca de este tipo de encuadernaciones (aparece así en mayúsculas en muchas de las referencias):

http://www.google.com/search?hl=en&lr=&q="acco COVER"&btnG=S...

http://www.google.com/search?hl=en&lr=&q="acco COVERs"&btnG=...

Binding Options
The documents are three hole drilled on the left side or on top, then ACCO covers (thick cover stock, with two pieces of wire attached to the front and back ...
www.artbookbinders.com/ClosingBooks/clos1.htm

A Few Notes on Formatting - Nicholl Fellowships in Screenwritign ...
Hard, slick Acco covers (with long metal connectors). "Permanently" bound scripts (ie, plastic spine binding). Commercial, "college paper" covers. ...
www.oscars.org/nicholl/format.html

craig-inside
I also purchased ACCO covers. After I received the master from Brian (on the Tuesday before the conference), I quickly wrote and added extra intro material ...
www.finseth.com/hpdata/craig-inside.html

MovieBytes - Screenwriting Contests & Markets Online
... The long, silver looping Acco metal fasteners that accompany the hard Acco covers are also disliked by readers, as they too tend to fall apart under the ...
newscripts.moviebytes.com/NewsStory.cfm?StoryID=420

Hope it helps!