Many later stock certificates have revenue stamps, so I don't think this is necessarily in the wrong forum.
Caveat: I do not collect stock certificates, BUT the fact that this is certificate number 1979 indicates that a significant quantity of these did exist at one time. With those potential numbers, I would call the dealer's opinion of "exceedingly rare" as puffery to sell his example. It does have very attractive engraving. A quick check of Google images locates this example numbered over 2700: