Think the Mod 53 was introduced in 1961. Since mine is a 4 screw, does that mean it was manufactured in 1961? Reading the categories, says guns made 1962 and later are 3 screws. Correct?
My four screw (SN K441478) shipped in June of 1961. S&W rarely (never?) made changes in absolute timeframes; they used up parts on hand until sometimes long after the order date of engineering changes. Yours was probably made in 1961 but a letter is the only way to find out exactly when it shipped and to who/where. The good Dr. Jinks will provide the month and year of a serial number to SWCA members on the member side of the Forum. Another good reason to become a SWCA member and which also earns you a reduced rate on the S&W letter cost. The M53s are great fun to shoot, enjoy.