Re: Iver Johnson Revolver Questions
this helps some, these three patent date were used together between 1907 and 1911. the only problem now is this span the second model black powder only (1896-1909) and the fhird model smokeless powder (1909-1941). the model name for your revolver is 'safety automatic hammerless revolver'. if the letter code is an "R" it will be a second model and if the letter code is "D" it will be a third model.
if it turns out to be a second model (black powder) it probably wont blow up in your hand but the firing of smokeless powder it it will hasten any and all wear on the internal mechanism and sooner than later it will get out of time and not be safe to fire.
if this is a third model it will make a good personal protection firearm but if it is a second model it should be retired.