5th paragraph here RP.
http://www.defensivecarry.com/forum/defensive-carry-guns/170706-smith-wesson-revolvers-post-them-all-5.html#post2854950
"that hammer spur style on your revolver is known as the "Speed Hammer" and was developed by Smith & Wesson to aid in thumb cocking the revolver for single-action use. It greatly increases thumb purchase on the spur over the older and more graceful ( but less positive in use) pre-war hammer spur style and made single-action cocking much more positive and speedy. The "Speed Hammer" was introduced simultaneously with Smith & Wesson's new "short-action" lock work which gave a shorter lock time from the break of the trigger sear to the ignition of the primer. This was accomplished by reconfiguring the hammer on it's anchoring pin so the fall was shorter. All this was a "big deal" in its day."
Wonderful firearm gw, one of the very best of breed imo.