Howdy
First of all, let's get the abbreviation correct.
It is SAA, which stands for Single Action Army. A lot of guys get that wrong.
Up until about two or three years ago Uberti replicas had what is often called a Four Click action, which functioned exactly the same as the action of the original Colt Single Action Army revolver. Hammer back about 1/8" to "safety click' position, second click is the half cock position which frees the cylinder to rotate for loading, third click is when the bolt pops up against the cylinder, and fourth click is when the hammer goes to full cock and the bolt pops into its locking slot in the cylinder.
Seasoned single action revolver shooters know never to completely load this old style of revolver with six rounds, because the so called 'safety cock' notch is very fragile. This photo shows the lockparts from a Colt. The upper arrow is pointing to the 'safety cock' notch on the hammer, the lower arrow is pointing to the tip of the trigger that fits into the various cocking notches on the hammer. Notice how thin the tip of the trigger is. It is so thin, that if the hammer spur receives a strong blow, the tip of the trigger may break off, allowing the hammer to be driven forward and the firing pin can strike and fire the primer of a round under the hammer. Accidentally dropping the gun on its hammer has been known to do this many times. For that reason, it is always recommended to carry a Colt or replica with the original design only loaded with five rounds, with an empty chamber under the hammer.
About two or three years ago Uberti changed the design of their single action revolvers to include a retractable firing pin mounted in the hammer. Not a frame mounted firing pin, this design normally retracts the firing pin into the hammer so that if the hammer receives a blow, the firing pin will not fire a round under the hammer. The firing pin only extends far enough to fire a round when the trigger is pulled. When the trigger is released, the firing pin retracts. The firing pin is still visible in the hammer, it just does not protrude quite far enough to fire a round. This newer hammer design is sometimes called a Three Click design because it lacks the 'safety cock' notch. As I say, Uberti introduced this design two or three years ago. For a while the earlier 'four click' Ubertis were still available, but they are rapidly disappearing from all the importers' inventories.
The Uberti revolver in Hawk's photo has not been available for a long time. It incorporated a safety block built into the hammer, but I have not seen one in many years. I used to have one, but have now owned it for a long time.
This is an Uberti Cattleman I bought used close to 20 years ago. It has the traditional Four Click mechanism just like a Colt. In order to be legal to be imported into the US, this model came with an extra long cylinder pin with two notches cut into the pin. Normally, a Colt has one notch that engages the transverse frame mounted spring loaded latch to keep the pin in position. With the Uberti pin latched at the front notch, the rear of the pin extends back through the frame and serves as an effective hammer block, preventing the hammer from firing all the way. With the pin latched in the rear notch, the rear of the pin no longer blocks the hammer from falling all the way. This device was only there to allow importation into the US, it is useless as an actual 'Safety' because disengaging it requires one to hold the revolver in one hand and pull the pin forward with the other hand. Not a very practical 'Safety'. I did what many owners of this model did, I bought an after marked pin with just one notch and replaced the OEM pin. Another solution is to grind away the rearmost 1/4" or so of the pin.
A note about 'the most accurate reproduction'. Many, if not most, of the Italian replicas have the old V notch rear sight of the 1st Generation Colts. This photo shows a Second Generation Colt rear sight on the left and the rear sight of my Uberti Cattleman on the right. 2nd Gen Colts had a nice, squared off rear sight notch that made seeing a good sight picture very easy. My Cattleman has a V notch, very similar to a 1st gen Colt. Not the easiest to sight with for old eyes.
This is the rear sight of a 1st Gen Colt. A very tiny V, probably smaller than the Uberti V.
I am pretty sure the SAA replicas made by Pietta still have the traditional 4 click action. Not sure what their rear sights look like. I am also pretty sure that some of the replicas, particularly those set up for Cowboy Action Shooting, have the squared off rear sight of a 2nd Gen Colt.
A word about importers, such as Cimarron, or Taylors and a few others. None of them manufacture firearms, they import those made by Uberti, Pietta, and a few others.
Finally, an editorial word about Four Click actions vs Three Click actions. If you watch Western movies there is usually a scene where somebody cocks his pistol very slowly, and the audience can distinctly hear and count the four clicks. Usually it is when somebody is threatening somebody. They always put this scene into the movie for effect. When I cock the hammer on a Colt, Uberti, or even a Ruger on the range, first off I have ear plugs in, so I don't hear the clicks at all. And I never cock the hammer slow enough that I can hear all the clicks distinctly. I have fired one of the new '3 click' Ubertis, when I cocked the hammer the sound was just a blur, no different than one of my Colts. The only time I can actually hear and count all four clicks is late at night when I am pretending to shoot the bad guys on a Western on TV with one of my Colts. Otherwise, the number of clicks is usually just an indistinct ratchet sound.