Pete;
The 1881 drawings are identical to those of US patent 246,195 issued Aug 23 1881 to H Pieper. The tubes under this patent were neither stepped or threaded. The holes through the block were bored on a taper, being larger at the rear. The tubes had a matching taper on the rear & were inserted in the block from the rear, thus the step, as the block was of necessity larger than the tubes. On those bbls having a smooth transition the tubes are stepped & thus inserted from the front. On my old Pieper, unlike the pictured Beretta, they only go approximately half way through the block & I suspect are threaded in. Inso far as I am able to discern the ribs, tubes, everything was assembled with the use of soft solder. There is no evidence of any brazing on the gun at all. I have not personally seen a lot of these guns, but of those I have & also pictures etc, all I have seen having the Original Diana marking seem to have had the stepped bbl construction while those marked Modified Diana have had the smooth construction. I have never known though whether the markings had anything to do with the bbl joining method or were just co-incidental.
