As to Old Model and Pre-War frames, as far as Uberti is concerned, the Old Model has a base pin retaining screw inserted from the front of the frame, and a rounded ejector rod head.
The Pre War Model has the cross bolt base pin latch and crescent ejector rod head.
Here is the base pin retaining screw on an Old Model:
And the round ejector rod head:
As for the Pre War, here is the crescent ejector rod head:
And a Pre War Frame, the cross bolt latch visible just behind the head of the base pin:
And, yeah, for you of sharp eyes, the ejector roda are on the same gun. I swapped then out after acquiring this revolver.