Bought this antique bottle years ago at a garage sale in Ontario. Still has dried residual coke in bottom of bottle. This Antique Coke Bottle has bottom stamped with IU (Diamond Shape with small D inside it) 61. Could be reading upside down, but diamond has a “dot” under it. Tried to look up bottom on Google Image, but nothing similar found. Thank you for looking at my post. I check my emails 1-2 times daily, but may be delayed due to health conditions, which require me to visit hospital.