Hard to tell, I think maybe a bit better than 40%. Honest wear... nice patina. I'm not a SAA expert by any stretch of the imagination... hopefully, someone with more knowledge will pop in and expand on my meager comments.
You can submit the SN to Colt Archive services for a letter here
. They charge $100 to research a SAA... and you get your money back, and then some, when and if you sell it.