Mark;
The shell lengths in the 1902 catalog would have been the 'Normal" length for the day. These would have been 12ga = 2 5/8", 16ga = 2 9/16" & 20ga = 2½". I am not positive if the 10ga at that point would have been 2 5/8 or 2 7/8.
Henri Pieper referred to his guns built as his original mono-block pattern as "Original Diana" & those built under a later variation as "Modified Diana". I have a Pieper hammer gun marked as Modified Diana & it has the steel mono-block (Pieper called it a steel breech piece) with twist bbls.
I think it likely those in the Sears catalog listed as "Diana Style" probably were just decaled up to that appearance & did not necessariy have either mono-blocks or twist bbls.
