Gents,thanks for the info. Great link. If I am reading it right my NID 20ga should be 2-3/4". My Ser# is 437888. Any way to tell what year it was made? How can I tell if for sure it is 2-3/4"?.I am not going to fire it much. Only going to use low brass bird shot.This board has been very helpful and I thank you all. Ed