LTDtwice,
I see that you are a new member of our forum, so, just to clarify what other members have said in response to your inquiry:
Based on the feedback others have posted regarding your father's gun, it appears that it may be enough of a rare/uncommon/early example that it would be worth spending $100 to have the S&W historians, look it up in the historical company records, and produce and send you a "letter of authenticity" that confirms the historical authenticity of this firearm that you have inherited.
For an early S&W firearm like this especially one that may have been only produced in very limited numbers, having this letter of authenticity will often enhance the value of the firearm far more than the $100 cost of obtaining the documentation from the S&W historians.
That is what Model19man means when he says this one is "worthy of a LETTER"
I'm sure that other expert members will chime in with more information.
Thank you for posting pictures of this revolver you inherited and welcome to the S&W forum.