I would be very surprised if there is no S prefix to the SN. First, prewar (pre-WWII) N-frames did not have SNs greater than about 62000 (no letter prefix). SN S1455xx would place yours as being from 1955. And your photo clearly shows that is the case, unless you consider pre-war to be "pre-Vietnam War." At that time, S&W catalogued yours as the ".38/44 Outdoorsman" target revolver, as you originally noted, not as a Model 1950. The "Model 1950" designation was used only for similar N-frame revolvers chambered in .44 and .45.