Here is the recall ref the safety/decock/sear/hammer (half cock notch) system:



SMITH & WESSON
MODEL 439, 459, 469, 539, 559, 639, 659 & 669,
9MM CALIBER, PISTOLS

RECALL: This warning is issued for Smith & Wesson 9mm Semiautomatic Pistols which were shipped from the factory between May 1, 1983 and February 26, 1986. Included are Models 439, 459, 469, 539, 559, 639, 659 and 669 but only with serial numbers in the following ranges:

A745000-A865000 and TAA0001-TAL9999

The pistols within the serial number ranges listed above must be inspected for function from the half-cock notch. The safety mechanism will function in a perfectly satisfactory manner in many of these pistols, as well as in all pistols with serial numbers outside these ranges and in all pistols shipped from the factory after February 26, 1986.

Every one of these models bearing a serial number within the ranges listed above should be carefully inspected by the owner for this special condition. To determine if your pistol has this condition, do the following:

Point the muzzle in a safe direction.
Completely unload the pistol. Check both the magazine and chamber to assure they are empty of live rounds.
With your finger off the trigger, operate the manual safety with the unloaded pistol fully cocked and fully uncocked so that you can recognize how the manual safety looks and feels when it is fully in the safe position. The hammer will fall from the fully cocked position into the "at rest" position when the manual safety is moved down toward a safe position. When you are thoroughly familiar with placing the manual safety fully in the safe position, place it up in the fire position.
With the manual safety in the fire position, place the hammer in the half-cock notch:

For the Model 439, 459, 539, 559, 639 and 659, put the hammer of your pistol in the half-cock notch by pulling the hammer to the rear slowly until you hear the first click and then releasing the hammer so that it catches between the full cock and the "at rest" position.

For the Model 469 and 669, put the hammer of your pistol in the half-cock notch by inserting an empty magazine and slowly pulling the trigger until you hear the first click and then releasing the trigger so that the hammer catches between the full cock and the "at rest" position.

With the hammer in the half-cock notch, push the manual safety down toward the safe position. If you can push the manual safety fully into the safe position and the hammer falls into the "at rest" position, your pistol does not require modification. If you cannot push the manual safety fully into the safe position or the hammer does not fall into the "at rest" position, your pistol is being recalled for modification free of charge.

Recalled pistols should be sent promptly to a Smith & Wesson Warranty Service Center for modification. Call 800-331-0852 for the name and location of the one nearest you or for answers to nay questions you may have. Law enforcement departments who have pistols, which exhibit this condition, should contact the Smith & Wesson Service Department to arrange for modifying the pistols.

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Ret. LE, FA Instr, S&W Armorer