That's the sort of error that a competent seller, who has to
catalogue the coin and should check its
types and legends against the
catalogue, really ought to notice and point out in
his description.
A buyer, however, will often overlook such an error if the seller doesn't point it out, for even a specialized buyer can't keep all the attested variants in
his head, and won't have the time and stamina to look up every coin in the
standard catalogues, or even to carefully examine the
types and legends of all the coins which at first glance look common, checking for unsuspected
legend errors or obscure typological variants!