This offer is good for the first 90 customers at each restaurant that present this White Castle coupon . In honor of their 90th birthday, if you are one of the first, you will get a FREE Original Slider every day through 8-31-11 with any purchase. In addition you will get a birthday pin to wear! They suggest if the location you visit has reached the 90 limit you try another one. If you like Sliders it's worth a shot!