I went to the Numrich site to get an ejector rod for my Official Police. They have 3 listings - one for the MkIII guns, one for Official Police, and one for Official Police E-frame. I don't have a MkIII, so how do I determine if I have the E-frame gun, or not? If it makes any difference, the stocks from my Python fit the OP perfectly, and the ejector rod has a removeable knob. Gun was made about 1967.