S-W (Sure Winner) Green Trading Stamps

For as long as I have had this packet of 1500 green trading stamps stored away, I thought they were S & H Green stamps. Upon looking at them closer I found out they are S-W Green Trading Stamps. With the stamps was a cardboard sign that says: Defend America We Give Sure Winner Green Trading Stamps. This makes be believe these stamps were issued during World War 2. The stamp says cash value 1 mill, sure winner, standard of perfection. I searched the internet for more information, but not much out there.