I don't really know of a sure way to tell the age. When I was about 12, I bought Igor. The Pet store lady told me that she wasn't too sure, but that she thought he was about 12 or 13. 14 years later, I still have igor. I have another turtle that I just purchased at christmas time. I think she is about 6 or 7. The pet store had no idea how old she was. She is about half the size of Igor though. Igor has always been the same size since I got him. I've read somewhere that you can count the line patterns on the bottom of the shell. Igor doesn't have anymore lines there, they're all worn down smooth. But Izzy does, I think I counted 7, but it's not really that clear. can't wait to see yertle. did you know there is a book series called "yertle the turtle"?