If it was a conversion, which I am almost to the point in believing it is not, it was very well done. The shotgun barrels would have been pulled out of the monoblock and the rifle barrels inserted.
The caliber is a standard european caliber and I have the dimensions of the case. It looks identical, within maybe a few thou, of the 45-100 Sharps. Guess I will order some cases from Buffalo arms and see how it performs