S&W started using the Triple-Alpha/Four-Numeric s/n system in 1980. Between 1980 and 1984 they used that and their previous s/n system, both. By 1984 they'd fully converted over to 3A/4N. Your's is the earliest 3A/4N I've ever seen. I think 1982 is right, but could maybe be early 1983. Any chance you still have the original box? It's possible there's a date code on it.