Raimey,
Another benchmark (of sorts) is the introduction of sideclips on the higher grade SxS Daly hammerless models. The 1902 SD&G catalog is the earliest I have found that mentions sideclips. Curiously though, the picture of the shotguns in the catalog above that description does not actually have sideclips. The 1903 SD&G catalog rectified that oversight.
As a guide, the introduction of sideclips comes pretty close to (roughly) serial #1000 (second series) which again happened in the 1901/1902 period. I have a another good date indicator in the 1899 year at ~#900 (second series). So the #1000 benchmark is reasonably accurate given those to date points.
All this assumes of course a relatively stable number of guns produced between the benchmark years which is likely a stretch, but also the best information I have barring any other benchmarks.
Ken
