Revelation of John 13:
16 And he causeth all, both small and great, rich and poor, free and bond, to receive a mark in their right hand, or in their foreheads: 17 And that no man might buy or sell, save he that had the mark, or the name of the beast, or the number of his name. 18 Here is wisdom. Let him that hath understanding count the number of the beast: for it is the number of a man; and his number is Six hundred threescore and six.
So there will apparently be six options for this branding: the mark, name or number of the beast either in the right hand or on the forehead. We can only speculate what that mark or name will be, but we do know that the number shall be 666. But how will this 666 appear? John saw it and he understood it. It is likely that John understood Hebrew/Aramaic and Greek. There is some evidence that Aramaic had begun to supplant Hebrew decades before the Revelation was written.
In the post mentioned above we did look at the Greek "XES" that represents 666 in that system:
The Greek letter stigma reminds me of the Superman symbol. In the film Man of Steel Superman said that the symbol means "hope," as in "they hope you'll all take the mark?"
There is little debate regarding how 666 would have appeared to John if he had seen it written in the Greek and seeing how that the letters were written to the "seven churches in Asia" it certainly is reasonable to presume that John wrote the Revelation in Greek.
Making the argument that John saw 666 in Hebrew/Aramaic is not so straightforward. If it was written in long form it may have looked something like "שש מאות ששים ושש", shesh meot shishim ve-shesh. Asking the reader to "count the number" suggests that the number John saw was a Gematria value, which means assigning numeric values to letters.
source: Deborah Jean Stearn, Unveiling the Mystery of the Last Days: Part 1 in the Sealed Till the Time of the End Series, 2012, pp. 24,25
In the Hebrew example above note that the literal meaning of vav is "nail." I have seen the Monster Energy Drink logo compared to the number of the beast on quite a few sites:
In this logo we have three vav characters that make up what is supposed to be a stylized letter M. Imagining these as three vav characters yields three number sixes, which is not literally the number of the beast, but those who designed this logo could be hinting toward it and I suspect that they are. These characters do also look like three nails and this is quite telling:
Triclavianism was one of the beliefs attributed to Albigenses and Waldensians, who held that three nails were used to crucify Christ and that a Roman soldier pierced him with a spear on the left side.
The three nails, as a symbol for the crucifixion of Jesus Christ, are also used on the coats of arms of Drahovce, Slovakia, Saint Saviour, Jersey, St. Clement Parish, Ottawa and in the seal of the Society of Jesus. source
There is our Jesuit connection. Note the three nails at the bottom:
Perhaps what John saw was the Arabic number 666 and the Holy Spirit gave him the knowledge of what it was. At this point in time no one can be certain of exactly what the actual mark, number or name of the beast will look like and it really does not matter. All will be revealed when it is revealed and if you are in Christ you can be sure that when you do see it you will know it.