It is now in the mail to another forum member.
In actuality it is just a real long trigger that increases your leverage. K,L and N frames all use the same trigger. The jogs in the lever are so that the extension added to the trigger clears the trigger guard.
I took a spare trigger I had removed the rebound slide toggle and welded on an extension similar to the on in the one toyman showed in another thread. the hand spring is still in the trigger and you must install the correct hand for your frame size. Then install in a frame. Need the cylinder stop and bolt to lock up cylinder, but do not need hammer or rebound slide and spring. Side plate needs to be on to fully support the trigger stud. Pulling back on lever is just like pulling the trigger, it trips cylinder stop and cylinder turns into position and the stop locks it up same as always. IF the ratchet tooth is long instead of the hand slipping by the tooth, the top chisel like edge on top of the hand will be caught against the high part of tooth. The hand is very hard and the ratchet is soft. Then the added leverage gives you enough mechanical advantage that the edge of the soft ratchet is peeled of by the top of the hard hand. Very similar to a hard cold chisel being drove against a small corner of soft steel. As the hands pivot pin is smaller than the trigger stud and only supported in one spot on the hand it should break well before the larger OD trigger stud which is supported by the frame and the side plate.
Ideally one could have several thickness hands for each frame size. Use the tool with thinnest hand until tool runs smooth, meaning it has shaved all the teeth as much as it is going to, then try your trigger and hand. If it goes your done. If not install thicker hand in tool and run it again.
I have had new guns or replaced a cylinder and found a hitch in the trigger right after the gun cylinder locks up, but before the hammer falls. The hand is against a slightly high ratchet tooth. If you simply dry fire it repeatedly, the hand will do just what the tool does and shave a tiny bit off any slightly tight teeth. That or a few passes with a fine diamond file and no more hitch. Occasionally you will find small burs on top of new ratchet teeth. The hand rubbing the side of tooth did it. A swipe or 2 on top of those teeth with a stone or fine diamond file cleans them right off. The ratchet teeth should and can be slightly lower than the center button around the tip of the center pin. That center button is what holds the cylinder's pressed back headspace. That is not the top of the ratchet teeth job. The fit between end of yoke tube and bottom of center pivot hole in cylinder is what holds pressed forward head space. The barrel is fit to the cylinder, not the cylinder to the barrel to get proper B?C gap
Revolvers are so interesting. Simple parts doing precision operations. All with just enough clearances to operate smoothly.
The trigger does 4 things when you begin pulling it back. It pulls the stop down as the hand begins to turn the cylinder, and also presses on the DA fly to start to rotate the hammer back. It also slides back the rebound slide. The front tip of the trigger releases the stop very quickly so it's tooth can pop up ready to ride into the lead in to its stop notch. The stop has a oval hole so it can slide out of the way enough to clear that tip when trigger is released. The DA sear clears the trigger and the trigger is begins to directly rolling the hammer back to near the end of it sear. As the trigger keeps moving the hand pushes the ratchet and revolves the cylinder to the point the stop pops into its notch and then the hand slides by edge the tooth and then the trigger releases the hammer to rotate forward and strike the hammer. Boom, the bullet leaves the case and jumps into the forcing cone and as it bridges that gap that the tiny bit of slack in the stop to stop notch fit allows cylinder and bore to become even more closely aligned as the base of the bullet is still in the throat as the body of the bullet begins to engage the rifling. Accuracy!
The amount of simple genius in the design is amazing. Toggles, springs, levers, axles and pins all working together.
The only real changes in how the action itself operates from S&W's very first double action top break revolvers to the current ones is modifications to how the springs operate the trigger, hammer, DA fly and hand. I simply can not imagine the absolute need for machining ability needed to make them 150 years ago. Rivaled only by watch makers IMHO