Hopefully a moderator can move this for you. In the mean time…
Have you got the revolver's original box with intact end label? We can decode a date with that.
You can also call S&W or send them an email with your serial number and they can nail down a date.
If I am guessing, I would say it was made late July to mid-August, 1988.
Of all the engineering changes of early 686 models, the dash-2 was perhaps the shortest lived and produced in the least volume. The 686-3 that was next was made in far greater volume.
Perhaps the other posters missed an opportunity:
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