What iPhone model is shown in Apple's Recycling video?
Judging by the guts of it, the size, and the finish, I am going to say that this is an
iPhone 6
It's too big and rounded to be a 5/5S series or earlier.  Assuming that it's not the iPhone 7 (which hasn't even hit the prototype phase), we can narrow it down to a iPhone 6 or 6S.  There is one slight difference between the two:

In our little video we see that it has only the iPhone name on it:

So, that's why I say it's an
iPhone 6