There have been previous discussions about how to disassemble the Master laminated padlocks.
I thought I should add this information: the easiest way to make sure you can reassemble this is NOT to grind or shear off the rivet heads flush. Instead take some time and remove the edges of the peened rivet, leaving a stump sticking up. Then pull the bottom plate off.
You can remove the peened edge of the metal with a "hollow mill" or carefully with a Dremel tool, just cutting the edge off the rivet, and then filing around the remains to leave the stump. This method should leave enough metal that you can reassemble the padlock by peening the remaining rivet that sticks out.
I haven't been able to find replacement case rivets for Master padlocks. If anyone has a source, please post.