The discontinued Hammer Safety was a shotgun-style safety that was fitted to the hammer directly under the hammer spur.   The safety was held in place by a detent ball and spring and was milled to sit flush with hammer when in the “off” position.  When “on” the Hammer Safety projected just over the edge of the hammer and prevented the hammer from retracting into the revolver’s frame when the trigger was pulled.  The Hammer Safety cost no more that a replacement revolver hammer, could be set up for either right or left hand shooters and could be removed by any competent gunsmith in minutes.  Regrettably, the Hammer Safety was developed just as the police revolver was being phased out in favor of the semi-auto pistol.  I had one fitted to a duty revolver many years ago and saw convinced to sell it to a fellow who was looking for a hidden feature that might safe guard his children should he ever fail to secure his weapon after work.  Of all of the revolver add-ons I tried over the years it is the Hammer Safety that I miss the most. It was simple, reliable, easy to flick on, reflexive to flick off and unobtrusive. I once had a State Trooper friend who was concerned that the holster I was carrying my duty weapon was set up for fast access and not for retention. I assured that the set up was a working balance between speed and access. Despite my assurances he continued to voice some concern. I removed the revolver, removed the rounds, we triple checked that the weapon was unloaded and I reholstered the weapon.  Only unknown to the trooper, I had flicked on the safety. Once the revolver was reholstered I invited him to snatch the weapon and pull the trigger.  I would make no effort to prevent him from drawing the weapon but he was not to quit until the weapon dry fired. He instantly snatched the weapon, turned to one side and tried to fire the weapon. The Hammer Safety prevented the hammer from retracting into the frame and therefore prevented the trigger from retracting. So intent was he on pulling the trigger that he failed to see me step forward and pop the gun out of his grasp. Then with a quick flick of the safety I pulled the trigger and dry fired the revolver a half dozen times. Point made I think.