ne of the most fundamental symbols in Magic (right up there with ) is the tap symbol. Since its original look in the Revised set over years ago, the tap symbol has seen three different designs. (Magic cards in the Alpha, Beta and Unlimited sets had no tap symbols, and instead had the word "tap" in their rules text. See the Beta Royal Assassin for an example.) To see the change in design of the tap symbol over the years, let's look at how Royal Assassin has changed from Revised to Fourth Edition to Eighth Edition.
As you can see (above if your eyesight's good, or below with less eyestrain), in the original tap symbol (as seen on the Revised Royal Assassin), it's a slightly tilted capital "T" -- standing for, of course, the word "tap." Starting with Fourth Edition in 1995, the tap symbol changed to the curved arrow symbol, with a black rectangle representing the tapping card behind it. This change to a more symbolic tap symbol made Magic cards more translation-friendly. Then in 2003's Eighth Edition set, it changed to the simple, straightforward, easy-to-see curved arrow, without the rectangle behind it. See below for high-resolution versions of the three designs.