S serial
ab7wh, that is probably a 1969 gun, but you cannot use the serial number to determine the month or even year. S&W did not ship in serial number sequence, so even if you found a gun that was one number before your serial number, the shipping date could be months apart or even years. The only way to confirm the exact shipping date is by requesting a factory letter (cost is $50). That will give you a nice, brief history of the model along with the shipping date and name of the store, distributor, or individual who received the gun. For a 29-2, it most likely went to a S&W distributor.
The S-serial numbers command a higher value for a number of reasons (some real, others perceived). Since S-serial guns usually shipped in the 1950s and 1960s, many people feel the quality was higher and quality control was better. I own guns from the 50s, 60s, and 70s and can tell you from my experience that the difference in quality between late S-serial and early N-serial guns is difficult to observe (and perhaps impossible to find). But, I will also tell you that I only own one N-serial gun (a birth year gun for me) and many S-serial guns. But for me, the reason is that I prefer the early 44 Magnums over the ones made in the 70s, 80s, and 90s.