I broke open an MLPS today and had a look inside. The thing is not full of a magical powder like I thought it was. It is just a set of contacts with different paths to tell the computer what position it is in. It seems like a very basic design.
http://www.perryjoshua.com/Exchange/mlps1.jpg
http://www.perryjoshua.com/Exchange/mlps2.jpg
http://www.perryjoshua.com/Exchange/mlps1.jpg
http://www.perryjoshua.com/Exchange/mlps2.jpg