The Smart Cover will not fit or work with the iPad1, unfortunately. The iPad2 has a number of magnets inside its case to secure the Smart Cover in place. Those magnets were not fitted to the iPad1, so the cover would not 'attach' to it.
In addition, the Smart Cover automatically switches the iPad2 on and off. It does this by having some magnetic field sensors inside the case of the iPad2 that detect when the cover is being folded back or being replaced. Once again, unfortunately, the iPad1 does not have those sensors.
Although a third party vendor might be able to produce a cover that *looked like* the Smart Cover for the iPad1, since the iPad1 does not have those magnetic field sensors, there's no way that this pseudo Smart Cover could turn an iPad1 on and off.
Tim
Scotland