It could be a 'factory' Smith speed hammer that has been modified, but the ad says the 'original' trigger and block come with the gun. It was converted to SAO after shipping. Bob Chow was known to have 'drilled' hammers to lighten, but I can't find any photos of his revolver work to compare.
I agree. It's also machined further down, I would think this modification with a much lower mass, could cause light strikes. How does it work.
It works because V is squared (E=MV^2). The lighter hammer picks up enough extra velocity to keep energy flat or even improved.
My 18oz ball peen hammer hits much harder than my 8 oz.
Only because you don’t swing the 8 ounce fast enough. The physics are pretty basic. The hammer mass is reduced by some amount and because of that the spring can accelerate it to a higher speed. The higher speed reduces lock time and that is desirable for accuracy. The higher speed also maintains total energy to keep the gun reliable.
C is a fixed V.
I’d be curious to know if the single action notch was reworked to make it a true short action. 
Just to be a nitpicker, I'll point out that Smith & Wesson called it a "High Speed" Hammer, not a "Speed Hammer." The box shown below is from a K-22 Masterpiece, but the box for the K-38 and K-32 reads the same way.
I’m a shooter, not a collector. I'd buy (depending on the price of course).
if we're talking about single action only triggers, I believe PPC revolvers must be capable of shooting double action. Unless USA PPC rules differ to the international WA1500 rules, double action must be used for all shots except those at the 50m line.I would wager it will shoot .38 wadcutters in nice tight clusters.
Lots of bullseye and PPC handguns were modified in different ways to do just that. Most have very nice triggers.
I guess I wasn't clear. I was trying to say that modified revolvers for shooting in different disciplines usually had very nice trigger pulls and were tuned to work very well for the purpose, single or double action. Of course that would depend on who did the work.
I agree. I should like to see how it is set up.
