Serial number.
The -2 will narrow it down to a range of years, may be a couple of years, or may be a couple of decades.
If you post the first 4 letters/digits of the serial number, I'll look it up this evening when I get home.
If you're interested, there's a book called "The Standard Catalog of Smith & Wesson" by Jim Supica and Rick Nahaus that has serial number information in it.
It just came out in the second edition, which greatly epxands the information contained in it.