many thanks guys for your reply,
I just received an email about this revolver
here's the answer :
You have an Iver Johnson Safety Hammerless DA Revolver, 3rd Model which was manufactured from 1910 to 1941. There are no records available to match the date of manufacture with the serial number. The patent date shoulc read: Nov.17, 08.
The Safety Hammerless was chambered in .22 rimfire, .32 S&W and .38 S&W calibers