Ok, I'll give it a whirl. The barrel raises suspicion since it should have some markings on the side of the barrel. Could they be worn smooth? Next, it is not a Police Positive. They had a shorter cylinder window in the frame. This one has the narrow (front to rear) grips, so if it is a Detective Special it is an early one, agreeing with '28 to '30. Those grips look like the proper ones, but I can't see the medallion clearly enough to say what it is. Could that eagle be a well worn rampant colt. Whatever it is, it is very special to have your Dad's duty gun.

Ken