More than dos centavos hombre. I always enjoy those much more knowledgeable/experienced sharing.
However, I must respectfully disagree on your conclusions.

The brass doesn't exhibit flow that I would expect from a flux tipped brazing rod. Quite the contrare as it shows a grainy pattern that I would consider consistent w/cast. The rib appears to have been cut w/Dremel cut-off wheel.

I think the rib was cut long and then scored w/cut-off wheel. The metal sheath is thin enough that it was easy to make a cut on each side to the score. This allowed fairly clean removal of the sheath from the rear exposing the cast brass. That was shaved down to fit.

Using the 1946 38 spl barrel I measure the length of the sight at the top of ther base. It is the same length as the sight protruding from the raised rib. Granted I have to include the rear area of the blade that has been notched. Likewise the height the blade from the top of the barrel is the same as is the width. Though that's not to say it isn't homeade to the same dimensions.

When I picked up the sidearm I asked my gunsmith how much it would cost to crown the barrel. Knowing how cheap I am he replied, "I'd shoot it first and see how accurate it is now." I like your crown suggestions though I'll gnaw on it for a while before committing.

Just because I think something doesn't make it so. You are probably right, yet I have to try to make sense out of what I see. Perchance a mirage. I'd be happy to share any of my original resolution pics for your scrutiny. If you'd care to take a closer peek at 1.7MB shoot me an e-mail.