Wedgwood mark their wares Seconds in the following ways:
Scratch through the back stamp
G2 Etched into the back of the piece
Green dots (Please note some unscrupulous dealers remove these using T cut especially on Jasper ware you can tell if this has been done if the base looks unusually clean and the imprint Wedgwood is blurry instead of clear)
Dints in the backstamp.
No backstamp at all.
S/S means special run of kiln for the Wedgwood Shops ie Shop Saleware this does not mean that the pice is seconds but it will be younger than your original pattern.
I hope that helps you :0)