Ok this method was spread around maplestory so let me teach you how.
A Permanent Nx Equip (non duped, original one)
1st. Setup a Mushy with the Perm Equip.
2nd. Add a Use item ( Potion. etc)
3rd. Go to a Potion Shop and fill up ur Use Inventory
4th. Close ur shop. ( You should get an error)
5th. Talk to Fredrick and click Retrieve to obtain ur items back.
6th. Spam click and ur Perm equip should be duped.
7th. Keep clicking = Profit?