on the right-side side plate (one is typically hidden beneath the top of the grip). located in front of the trigger guard.
Some 4-screw guns from 1957-1958 still have serial numbers that overlap with late 5-screw ranges. The only way to verify is physical inspection. If your gun has a serial number indicating 1957 but lacks the cylinder stop screw on the front strap, it is a 4-screw. smith and wesson 5 screw serial numbers
| Model | Caliber | Frame | Serial Range | Year Range | Screw Count | | :--- | :--- | :--- | :--- | :--- | :--- | | M&P (Pre-10) | .38 Spl | K | C 1 – C 460,000 | 1948-1957 | 5 | | .357 (Pre-27) | .357 Mag | N | S 62,000 – S 139,999 | 1946-1957 | 5 | | .44 Spl (Pre-24) | .44 Spl | N | S 62,000 – S 94,000 | 1950-1954 | 5 | | K-22 Masterpiece | .22 LR | K | K 1 – K 260,000 | 1947-1957 | 5 | | Terrier (Pre-32) | .38 S&W | I | 536,000 – 619,000 | 1946-1952 | 5 | on the right-side side plate (one is typically