Howdy
http://www.coltsmfg.com/cmci/historical.aspThere is a link you can click on the right side to find out all the information. A letter for a SAA starts at $100. If it is your great-grandfather's Colt it is probably a First Generation and letters for them start at $150.
I don't know why Colt charges different amounts for letters depending on the model, but they do. With the letter you will get information on when the pistol was shipped from the factory, and where it was shipped. You will also get information on the original configuration of the pistol as it was shipped, stuff like barrel length, finish, etc. I lettered one of my Colts and found out that it actually left the factory with a 12" barrel, even though it now has a 7 1/2" barrel.
If you want information right over the phone, Colt charges more for that too. When I lettered my Colt a few years ago it took almost a year before I got the letter.
It does come on fancy, shmancy paper with a raised seal to make it official, useful for proving the provenance of historical guns.
By way of contrast, S&W charges $30 for a factory letter, for any model they ever made, with the same type of information, also signed by the official company historian. The Smith letter just comes on regular paper, not the fancy paper, but it is just as historically recognized as the fancy, shmancy Colt letter.
A rip off if you ask me, but maybe worth it to you for a family heirloom.
If all you want to know is when the pistol was made, post the Serial Number here and I can look it up for you, so can lots of other guys. For free.
If you post the SN on a public forum like this, be sure to substitute an X for each of the last two digits. so 123,456 would be 123,4XX. That's close enough to figure out the year. Don't post the complete SN on a public forum.