It's a die by Pretty Pink Posh -
here at Ellen Hutson for example. It cuts the tag and the little windows in one.
With a bit of patience though you could do it with a small square/rectangle die and a larger tag die cut if you won't do it often enough to make it worth buying the die. Lay the little die onto the tag and hold in place with a bit of low-tack tape then put it through your machine. Move the die to the next position and repeat until you've cut all the little windows.
HTH!