I agree with Marrakai. It doesn't look like the work of any of the makers he mentioned.

The flanges to the barrels are part of the shoe-lump construction and are brazed on. The presense of these doesn't automatically mean that the barrels are shoe-lump though. Some chopper-lump guns have them as well. On the chopper-lump guns, the flanges are integral and are just filed up that way from the blanks. On three otherwise identical A. Hollis & Son .450/.400 rifles, all with chopper-lump barrels, Rusty's, and I think Bobc's, have those. Mine, the latest of the three, doesn't. I have no idea why they did it that way on the chopper-lump guns.
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