Thanks Bill and George. I looked up an article in DGJ (Vol. 18 Issue 2) that shows a 10 bore Mullin being used to hunt Tundra Swans. Now that's using the old girl in style! The article suggests that the particular gun in question was entirely finished in England. Apparently they imported finished guns as well as unfinished barrels and actions?
I find this era of custom shotguns built on imported (I assume Birmingham) parts very interesting -- Golcher and the Kennedy Bros. in St. Paul, MN as well as the Mullins. Do you know of any good books on this subject?