Myth

It depends what valve prices it at. If it goes out as a mid range set than it is probably be 5 common/uncommon, 1 rare (probably mask), mythical back, and 1 rare/mythical (taunt).
If valve puts this up on the higher end than the taunt will be mythical, back legendary, mask rare, and everything else common/uncommon with one or both the weapons posibly as rares.

There is really no way in knowing till it actually comes out. The taunt and back will definitly be the highest ranked in quality assigned; though, the taunt will be worth a bit nomatter what quality it gets.