I sent SB three different paradox style bullets, two in the 770gr range and the 860gr ( I didn't have these molds in 2004). I was surprised when I found out they had settled on the 860gr bullet. I don't know if it was because it was the only bullet that would easily regulate in the heavy gun or it was at the wishes of the Nowatny's owner who supplied me with the 860gr mold. There was a subsequent hunt where the gun/cartridge combo was used on elephant, in that case I really think the added velocity of the standard Super Magnum Explora cartridge would have been useful.
I know the paradox drilling was for sale at Hallowells for quite some time but also somewhat mis described. I don't remember it as being scoped at that time either. The gun has 2 3/4" 12 bore chambers if original don't you believe it had to have been for some magnum loading?
Did it have fairly standard looking 7 groove paradox chokes?