I had US Patent #488,366 issued Dec 20, 1892 but as it does not apply to bbl joining thought perhaps I was missing one. My old Pieper is marked Modified Diana, has twist bbls screwed into the steel breech & does have a joint in the rib at same location as bbl joint. It has double underbolts & conventional style Doll's Head rib extension. Since Steve's Bayard does not have rib joint, that may not be a good indicator. However the seller stated the bbls "Were not Sleeved" & as a pattern is visable through the bluing I do not believe those to be joined by the Pieper Breech Piece (Mono-Block) method but simply one piece bbls given that appearence. I have not seen a lot of Piepers, but of those I have seen or seen pics of, those marked Modified Diana had the bls stepped down & threaded & screwed into the front of the block with a flush transition, while those marked Original Diana had the step with unthread bbls being inserted into the block from breech.
