butlersrangers wrote on Jan 28^th, 2019 at 8:09am:

I believe an early front barrel-band has the inside contour, that I roughly 'colored' in red.

If the only difference is the radii in the corners near the thread that could be a tooling change during production. The sharp edge on those old tool steels would have been hard to maintain. Adding the radii to the broach would have made the tool last longer and during the tools life it easier sharpen. Each sharpening during the tools life would have made the radii larger. Maybe this piece was made with the first tool before a change was made.

If I was doing the fitting this to a reproduction stock it would be so much easier to take the corners off the stock compared with the time and expense to square up the corners in the barrel band. You might look inside the band and see if the tool marks indicate original work or a later modification.