They had some in 44-40 and 30-30 as well. Midway had a great deal on the 30-30 stuff a couple of years ago, when they were discontinuing it.
It was made to commemorate, what would have been John Wayne's 100th birthday.
I have a box and a half of the 30-30 ammo but it's not marked "DUKE" like you described. Darn, I wish it were... The ammo was given to me and unfortunately the empty brass was not in the box with the loaded ammo.