I have tried to see if your revolver has a screw at the top of the side plate on the right side. It appears to be there but I cannot be sure. If the screw is there the gun predates 1955, the year S&W engineered that screw out of the gun. If in fact the screw is there then the gun is properly classified as a "Pre 10". The Model 10 designation was applied in 1957. The first few numbers of the serial number, including the preceding letter, would be very helpful in dating your revolver.
Joe