Hi Don,
Copper spark plugs mean the core of the center electrode is copper - to improve heat dissipation. It doesn't refer to the firing end of the electrode, which is still steel alloy. Others here speak of platinum and silver and iridium, which are the metals used on the firing end - and may also have copper cores.
The part number I gave is the correct one for NGK copper core. You can also check their website, which is excellent, for more info, and another sparkplug option, the V-power.
Rhys