The Field gun illustrated is either a 10.G incorrectly stamped at the Birmingham proof house as a 12.G or a gun made in Belgium with fraudulent, incorrect, Birmingham proof marks.
My opinion is that it is a 10.G of Birmingham origin.My reasons are as follows:
1/ The gun is typical of the export guns made by the Birmingham trade in the 1880-1900,s A very similar, "export gun", is pictured on page 412 of W.W.Greeners book," The Gun."
2/ The application of proof marks to the barrels, rather than the barrel flats, was a practice used in this era by the Birmingham trade and the proof house on guns destined for export.
3/The finish on the gun is superior to that seen on Belgian guns imported and marketed by Folsom.
As for the possibility of opening up the bore of a 12.G that has barrels with the normal outside 12.G profile,it is simply impractical.The net result of an attempt at this magnitude of bore enlargementwould be; thin barrels at the proof diameter & paper thin barrels, approx; 7-8 inches from the muzzle.I Cannot believe a gun modified in this manner would have any prospect of passing legitimate proof!
As recommended by others I would not consider firing this gun until a competent gunsmith has checked all barrel dimensions.
A possible maker is:
William Field, 1881 @ 118, Unett Street, Birmingham. William field is identified in published records as being the manager of the Field Rifle Co; Birmingham 1885-1898.
