The canolo is the front placket.

see:
http://www.shirtsmyway.com/shirtspedia/dress-shirt-placket.p...

There are many variations - noy just the two listed in your document - see here

http://gentlemansway.com/the-dress-shirt-anatom/
where it says:

The front center placket is the piece of material on the front of the shirt where the buttonholes are placed. In the past, it was a separate piece of cloth sewn to the front, but today shirt makers often fold the edge of the material to form the placket. It gives the shirt a defined center and makes a clean finish where the shirt sides join to be buttoned. Most shirts have six buttons, or for taller fits, 7 buttons. Other variants of plackets are the Bluff front, Fly front and the Twin Stitching front.

Canolo coperto is a hidden placket - see

http://stylecrave.com/2010-03-30/dunhill-mitred-placket-shir...


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Note added at 2 hrs (2010-06-17 10:39:29 GMT)
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concealed placket also for canolo coperto

see

http://www.squidoo.com/shirt-placket