I will be happy to be corrected, but AFAIK, IJ never put the transfer bar on their solid frame revolvers, only on their top breaks, and post-war ads for the solid frames specifically say "does not have the Hammer the Hammer safety device."
According to Goforth, the Type I was made from 1900 to 1915, and the Type II from 1915 to 1941. The date usually given for the IJ change to smokeless powder is 1909, so if a change was made in the Model 1900 at that time, its outward appearance was not changed.
Jim