Vent ribs were available as factory alterations to guns built with standard ribs. Brophy's Plans and Specifications book has drawings for the special rib extension that was required to mate with the original flat rib frame. Ejectors would have been an available option on guns made after 1901. I have a 1906 grade 2, two barrel set with crown steel barrels and ejectors, along with a straight grip stock that was not listed as an option in the 1906 catalog for a grade 2.