I'm thinking the serial is what he gave, and the BDZ guns were May of 1989, according to Supica. I don't trust the numbers tables a whole lot. Not sure what the date you're seeking will be. The dates in the table can mean anything. Usually we accept them as the date shipped from the factory. That can also be a date they were in production, a date they were put into the "vault" at S&W.
But the bible says 5/89.