M101-5s and the closely associated M101-4s came with several different backs.
You can find a little more information here:
http://www.oldcardboard.com/m/m101-5...?cardsetID=965
You will also find a link on that page for a
List of Backs (w/Rarity Details) that will detail which backs were distributed with M101-4s and M101-5s respectively.