So Chris from S&W was very helpful in getting the production codes and made dates for the 6 3rd gens I own. Ended up sending it all in an email due to the number of guns. The 5903 which I should be able to pick up tomorrow was made 5/29/1990 with product code 104042.

My oldest 3rd gen the 3906 is from 6/17/1989, and the newest is my 3913 at 4/20/2000.