Why do some 1 frame guns weigh more than others?

[SXS OHIO]

I have been looking for a DHE or DH 16 Must have its skeleton but plate and modern dimensions. I want the smaller O frame. It is 1/2 lb lighter but also feels smaller in the hand when grasp around the action. They are less robust and to me this is also important. I also need the gun to be stocked high say 1 1/4 X 2 1/4 no more than 1 3/8 X 2 3/8, would like 28" tubes that have choke minn of .005 in the right barrel and .010 in the left, they can have more choke but no less. Gun should be in very good original condition and have no issues. A gun like this is hard to impossible to find and will not be cheap. I have only missed one that fit this description and it was listed for 12,500.00 It was sold during the first week listed. I had called after it was sold. Never have seen one like it since...)-: SXS ohio....