Christopher,
The latest Smith I bought (a month or so ago) has a new firing pin system. This is an N frame--large, if you don't know the designation. This was a new twist, as a pal had bought an N frame just before that which had the traditional hammer mounted pin, whereas mine had a frame mounted one. Presumably, this signals a switch in the entire line to a new firing pin system (?).
My J frame Smith is a few years old and has a frame mounted firing pin--I honestly haven't checked to see if this was always so for the little framed revolvers, but the others (K through N frames) have had hammer mounted pins "forever."
Traditionally, (prior to the Ruger transfer bar system) DA sixguns have had "rebounding hammers" which meant that the hammer didn't rest on or touch the firing pin unless the trigger was fully depressed in the firing mode. This is contrary to the traditional single action design which necessitated the "load one, skip one, load four, cock and lower hammer" routine for the SA's to get the hammer onto an empty chamber.
[If someone can shed some light on the new frame mounted firing pin system, as well as the rear groove on the trigger, I'd personally like to hear about it.]