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Revised (3rd Edition) was the last edition to NOT have the copyright line under the artist's name at the bottom of the card. If you have a white-bordered card with only the artist's name at the bottom, then you have a Revised card.
Edit: Unlimited is also white boardered. As acfranks pointed out "If there is no black keyline and the colour frame has a "bevelled" edge, then it's Unlimited edition." Revised is also the first edition to use the tap symbol.
Only if there is a black keyline around the edge of the card's colour frame. If there is no black keyline and the colour frame has a "bevelled" edge, then it's Unlimited edition.
That's true. Unlimited was far less common than Revised, so that did not come to mind. I'll update my comment.