Respectfully,
I would not shoot this thing on a bet, no matter who inspected it. If it has been bored smooth, standard .547 inch bullets won't fit it properly. The modifications, by God knows who, thinned the barrel. The metal work is malleable iron which is now over 150 years old. And, it was clearly used hard after it was turned into a fouling piece. How much are your hands and eyes worth?
Regards,
Don Dixon