According to a video found here, Shoebat claims he saw this in the Codex Vaticanus, which dates to the 4th century and is one of the two oldest complete New Testament manuscripts still surviving. There are a couple of problems with this claim.
First, like all other known manuscripts from the 8th century and prior, Codex Vaticanus was written in all uppercase Greek letters. Shoebat's claim relies on lowercase letters, reversed and rotated. Second, Vaticanus does not include the book of Revelation, which at the time was still not universally accepted as Scripture.
However, the Codex Sinaiticus, the other surviving 4th century New Testament, does include Revelation. Codex Sinaiticus can be found online here. Here is the page with Revelation 13:18. You can locate the verse in the box on the right, highlight the word, and the manuscript will zoom in on that word. Not only does Codex Sinaiticus use all caps, it spells out the words six hundred sixty six: εξακοϲιαι εξηκοτα εξ.
There is one older manuscript--papyrus 47 (𝔓47), dating to the 3rd century--which includes some chapters in Revelation. 𝔓47 can be found online here. Revelation 13:18 can be found on this page. The number 666 is in the 9th row down, near the left side, the three letters with a bar over the top to indicate a numeral. Again, they are all uppercase.
I don't know what manuscripts Mr. Shoebat was looking at, but they certainly weren't the originals, they were not the oldest manuscripts available, and they likely were not even ancient.