http://www.adrbny.com/dr_profile.jsp?cusip=640747101
this will give you more info on NPTMY.
yes its an ADR, incorporating 1 adr for 10 NMS.
its rise this last 12 months is attributed to 2 things - the rise in NMS price, and the rise in the $A.
the price quoted simply shows the equivilent value of NPTMY compared to NMS.
they have never traded.