I would like to recommend a book: THE BRITISH BULLDOG REVOLVER; THE FORGOTTEN GUN THAT REALLY WON THE WEST by George Layman
The various makes and models of Bull-Dog are covered, including Belgian, English and American. The Bull-Dogs made by Forhand & Wadsworth are a major focus of Mr. Layman's book. But not alot of info about IJ and H&R Bulldogs.
F&W made these with and without the company name. Some F&W's are marked INDIAN BULL-DOG. Unlike Belgian made Bull-Dogs, I have found that most F&W Bull-Dog parts are interchangeable within the same caliber. I have found the loading gates and ejector units to be the same on all .38 and .32 F&W Bull Dogs.