If I understand your question correctly, the SINGLE ACTION trigger pull on a S&W Revolver is usually between 3.25 - 4.0 pounds, very smooth and creep-free. Many are incredibly great right out of the box. Without a trigger pull scale or actually feeling the pull personally, we are just guessing what yours really is - but to someone not use to OLDER high quality Smith Revolvers - yes, they are terrific triggers right out of the box - one of the S&W "claim to fame" features.
SINGLE ACTION is when you manually cock the hammer back and pull the trigger to fire the gun. DOUBLE ACTION is where you simply pull the trigger and the trigger rotates the cylinder, cocks the hammer and fires the gun. The DA pull on a typical Smith is somewhere around 10 - 11 pounds.
If you think yours has an excessively light (hair trigger) SA pull, get it tested and checked by someone with a trigger pull scale and know for sure. If it winds up to be too light have a Gunsmith look at it. Who knows what was done to an old revolver over the years when the history is unknown.