Howdy
According to The Standard Catalog of Smith and Wesson, the Model 19-5 was first produced in 1982 and the Model 19-6 was first produced in 1988.
It is often tough to pin down the year of manufacture of a S&W by Serial Number because they were not always shipped in SN order, and sometimes the factory jumped around with the Serial Numbers. According to SCSW, serial number AHA 0667 was produced in January of 1985. Serial Number prefixes AHS through AHT were produced in 1985. By November of 1985 the factory had moved on to ALA through ALC. So 1985 is a pretty good bet.
That's the best I can do. For more specific information you will have to send for a factory letter.
