M57 vs M58 Barrel Differences

[Vettepartz]

Looking through my spare parts, I find a brand new 4" barrel that is marked 41 magnum. It does have the groove cut for the pin that goes thru the frame. It is a shiny blue. Is there any differences that would distinguish a M57 from a M58?

 

[erikpolcrack]

At least with the ones I'm familiar with, the Model 58 barrel would have no shroud for the ejector rod, whereas the Model 57 would probably have a half shroud.

 

[A10]

What Erik said. Plus the front sight will be low profile due to the fixed rear sight cut into the frame. A picture would make it obvious!