Argo;
Do you know what the muzzle diameters of this gun (#19286) are? it was originally proofed as an 11 gauge which means it would accept a .751" plug gage but not a .775" one. At reproof, it was proofed with 19.4 mm bores (.764"). At reproof, only the left flat is marked choke. "IF" at original proof, the barrels had less than .008" of choke they would not have been marked not for ball, even after 1875.
There is one other scenario & I truly do not know how this was handled. Original proof was for 11 gauge. Chamber was not marked, only the bore. Let's assume the .763" bores at re-proof were "Original". "BUT" the proof house did not actually measure the bore size at that time, only knew it would take a .751" plug but not a .775" one. So how did they determine at what muzzle size to mark "Not For Ball". My "Guess" & this is only a guess, is they had plug gages made up .008" smaller than each gage size. This plug would have been .743" diameter. It could thus have had about .020" constriction, but would not have needed to be marked as it would be safe with a ball intended for an 11 gauge bore. It would not have been safe with a ball intended for a 10 gauge bore, but nothing on the gun stated it was, in fact, a 10 gauge. Even though it chambered a 10 gauge shell, the bores were 11 gauge & so marked. Just a little food for thought.
