The first topbreak Hammerless guns were made in 1886 and bear pat dates in the late 1880's The patent granted to IJ was applied for by R.T. Your markings Check to see if the Mass is followed by the letters USA The 'H' can date it but the same data was used on several models,The first use of the letter h that I come across on a 38 S&W is on a model called the Safety AutomaticRevolver Hammer model(Automatic has to do with extraction.not rate of fire) On the 38 version that started in 1918 and went on thru to 1941 when WWII ended most civilan arms production Be advised that there are special cleaning requirements for blackpowder.Standard solvents and oils will not do it right and may lead to damage.A quickie cleaning can be done with a 15% solution of Windex with Vinagaer in distilled water.brought to a boiling point.flushed with clean hot water and flused with WD-40.The same windex mix can also be used to protect your fired BP neutralizes the chemicals formed on firing BTW it is a Do it Right Now event.even waiting overnight can damage your gun and brass Pitchford is incorrect.that would be FITCHBURG, Mass.That was their original home The revolver you discribe made in 22 rimfire.32 S&W and 38 S&W(which is not any form of the 38 Special and does not interchange with it.If you wish to fire it.you can get pressure proper ammo from either Blackpoweder loaded or smokeless loaded to extremly low pressures.

Iver johnson top break smokless powder