Board Thread:Game Discussion/@comment-5722943-20130704024103/@comment-11612571-20130711125530

Actually, you need to level up the armors to level 35 to unlock the plus version as those are boss armors.

Also, I would like to say that you are very lucky to get the BKal from a chest. I did see a friend of mine who has it at level 35.

I guess it is possible to get from a chest, just depends on luck.