If it's an SP, the first duplex AC outlet (next to the power cord) is a ground-fault interrupt (like the one in your bathroom, with a reset button?) This type outlet is only used on the SP, because in a "Balanced Power" device, there's no "real" ground ;--)
There should also be a little silver tag on the back between the power cord and that first duplex outlet, which has the model (SP) and the ser. no.
There should also be a little silver tag on the back between the power cord and that first duplex outlet, which has the model (SP) and the ser. no.