Well, when was your grandfather born? Obviously, if he was born in 1906-1907, it's unlikely he is 5-6 years old in the photo! He looks under 2 years old to me. Do you not know when your grandfather was born? If not, it would probably be easier and more accurate to find that out and determine the year of the photo based on his birth year/age than it would be to try to narrow down the year of the photo based on the scene and then guess at his birth year based on that.