I have a Iver Johnson Model 1900 22 Cal pistol s/n 19766 stamped on the trigger guard and also on the frame under the handle. It has a 7 round removable cylinder and a 1-3/4" barrel. On the top of frame is stamped IJDouble Action & Model 1900. I got the pistol from my grandfather after he died 42 years ago. Any idea on when it was manufactured