Hello, I am new to this forum. I recently received a S&W model 36 revolver. There are no dash numbers in the model number. It is a 38 special, 3" barrel with fixed sights. The s/n is 614592. It also has 3 screws. What is the approximate age of this revolver? Does this revolver have a frame designation as well? I wanted to change grips but most websites ask for the frame size. Thanks.