Volumes have been written covering speculations on the nature of the mark of the beast. Here is one such article claiming that the Mark is Islam. Regardless of whether or not any one speculation is correct, it is reasonable to make such assertions if one is attempting to remain true to Revelation 13:18 as a person "who has understanding".
From Barnes' Notes on the Bible we have: (d) that the use of symbols, emblems, hieroglyphics, and riddles was common in the early periods of the world; (therefore it makes sense that the mark would be cryptic.)
Rosenmuller said, "The number indicates a man, or a certain race of men."e.g. homosexuals or muslims?
That which is proposed by Rosenmuller, however, meets all the circumstances of the case. The idea is, evidently, that the number indicates or refers to a certain man, or order of people.i.e. those who accept homosexuality as legitimate.
Next we will look at why homosexuality strongly competes for the title of the real mark of the beast.