It's in the Tampa 2 Nickel playbook only in M18.
I'm assuming the side without the nickel back plays the normal cover 2, but that the nickel side plays some kind of match coverage between the nickel back and the outside corner. I just don't understand how it works, how those two (and perhaps the S on that side) coordinate their coverage.
Can you offer more detail there?
And is this designed to be run with the nickel back and outside corner on the field or boundary side, or does it matter?